UNDERWATER CAMPAIGNS
Laws of Chaos
Explore the wonder and danger of underwater campaigns
for the world’s greatest roleplaying game
UNDERWATER CAMPAIGNS
DANIEL CHIVERS & MARCO BERTINI
Author’s Note Credits
“Many characters miss out on unlimited amounts of wealth and Lead Designer and Author: Daniel Chivers
adventure because they can’t swim. Oceanic adventures are Art Director: Marco Bertini
challenging for medium- and high-level player characters ... Graphic Design: Davide Ruini
without the proper equipment, a group’s first sea voyage is Editing: Simon Collins
likely to be its very last. This keeps gamers from utilizing the Cover Art: “The Great Escape” by Todor Hristov
ocean’s full potential in the campaign.” Internal Art: All art purchased and/or used with permission, by
– Todd Mossburg (Dragon Magazine #116) various artists to include: Adobe Stock, Shutterstock, Daniel
Comerci – danielcomerci.com; Some artwork © 2015 Dean
I have always been fascinated by water and how much of the ocean we Spencer, used with permission; Enmanuel “Lema” Martinez;
still do not understand. When I started making underwater supplemental All rights reserved; Empty Room Studio; Graindfailure; Hjalmar
rules for Dungeons & Dragons I wanted to stay away from surface Wahlin; Joyce Maureira; Marco Ortiz Walters; Pixabay.com;
water (ships, storms, mist, etc.) as much as possible and focus on the Publisher’s Choiche Quality Stock Art © Ricky Hershey / Fat
underwater locations, creatures, and marvels -- some natural, some Goblin Games. The Dungeon Masters Guild was used as a
redesigned based on past fantasy I’ve read, and some completely new source for some of the art. All art taken from there is owned
creations. I tried to find all the relevant mechanics that already exist in by Wizards of the Coast and is used with permission under the
Dungeons & Dragons and either expand upon them, modify them, or Community Content Agreement for the Dungeon Masters Guild.
offer variant rules. I also tried to draw as much as possible from nature Version: September 2022
and if parts of this work read like National Geographic, then I apologize
and feel free to gloss over those sections. I know that I have a well-
deserved reputation for overly clunky and mechanical rules so if you
are using a mechanic of mine and it is slowing your game down and
not improving it then stop using it. I will be forever happy knowing that
something in this work inspired you and your campaign.
Each relevant section with already established rules will have the
established rules listed first and I will reprint or paraphrase to keep
you from flipping between different books or digital platforms.
Creatures listed in other works will have their source and page
number listed but I will not be reprinting most of them here. As an
added note, the most relevant underwater resource for Dungeons &
Dragons 5E in print is Ghosts of Saltmarsh.
A reference to a creature’s statistics will be shown in bold. To prevent over
100 individual book references, all aquatic creatures and their reference
and page number can be found at the beginning of Chapter 7. If a
creature is referenced and it is not aquatic then its reference will be listed
in parenthesis after its bold name if it is not found in the Monster Manual.
On the Cover
Baxtite escaped Carceri only to find himself at the bottom of the deep
ocean. He now struggles to reach the surface dragging behind him
three farastu who are desperately pulling on his chains.
DUNGEONS & DRAGONS, D&D, Wizards of the Coast, Forgotten Realms, Ravenloft, Eberron, the dragon ampersand, Ravnica and all other Wizards of the Coast
product names, and their respective logos are trademarks of Wizards of the Coast in the USA and other countries. This work contains material that is copyright
Wizards of the Coast and/or other authors. Such material is used with permission under the Community Content Agreement for Dungeon Masters Guild.
All other original material in this work is copyright 2022 by Daniel Chivers and published under the Community Content Agreement for Dungeon Masters Guild.
Contents
Glossary 4 CUhndaeprtwerat2e:r Campaigns
Chapter 1: 18
Underwater Locations
6 Lure...............................................................................................19
Fantasy Resources ...................................................................21
Water and Traps........................................................................... 7 Adventure Hooks.......................................................................21
Oceans and Seas......................................................................... 9 Underwater Encounters...........................................................22
Shipwrecks................................................................................. 10 Marble Path to Immortality.....................................................32
Civilizations Beneath the Waves............................................11
Underwater Wonder..................................................................13 CDhifafpictuerlt3i:es and Oddities 34
Unique Underwater Locations...............................................14
Max............................................................................................... 14 Water Hazards - Natural..........................................................35
The Odd Path (The Odd Network).........................................14 Diseases and Water..................................................................39
Water Hazards - Supernatural...............................................44
Undead Hordes..........................................................................45
CUhndaeprtwerat4e:r Combat 46
Three-Dimensional Combat....................................................47
Feats Underwater......................................................................48
Skills Underwater.....................................................................48
Chapter 5: 50
Underwater Equipment
Armor...........................................................................................51
Water Damage............................................................................52
Wealth..........................................................................................52
Magic Items.................................................................................53
CMhaagpicteUrn6d:erwater 56
Damage Types and Water........................................................57
Spells............................................................................................58
CChr eaapttuerre7s: Underwater 68
General.........................................................................................69
Creature Actions........................................................................69
Colossal Creature Size............................................................70
Bestiary........................................................................................72
Chapter 8: 126
NPCs and Personalities
Appendix A:
New Warlock Patron, The Pale Lady 150
EAxpcpeenptdiioxnBa:l Fish Generator 152
Inspiration and References.................................................. 155
Glossary Coral
This work includes some words that you may or may not be 1) A hard substance that is red, pink, or white, and that
familiar with. I have tried to be true to the natural world to forms on the bottom of the sea from the bones of very
reduce confusion, but this is a work of fiction and fantasy so small creatures.
an observant reader, especially one with a good understanding
of the natural world will see where I bent or broke a few rules. 2) Coral can also refer to the creatures that build coral, which
I used the Oxford Dictionary version of the English language comprise hundreds to thousands of tiny coral creatures
whenever possible to describe a word listed below. called polyps. Over time these coral communities create
coral reefs.
Abyssal Zone
Crustacean
The abyssal zone of the ocean is the layer from 13,000 feet
deep to roughly 20,000 feet deep. An arthropod that is usually aquatic or amphibious.
Ammonoid Ecotone
For this work ammonoid and nautiloid are synonymous. Feel A region of transition between two biological communities.
free to use ammonite, ammonoid, nautiloid, nautilus, or “weird
spiral thingy,” as you see fit. Note that some of these creatures Estuary
come in straight configurations as opposed to the iconic spiral
that is normally associated with them. The tidal mouth of a large river, where the tide meets the
stream. These areas are a great example of an ecotone and
Aquatic all of the amazing things nature can (or must do) to survive in
such an area.
Growing or living in, on, or near water.
Hadal Zone
Arthropod
The hadal zone is the layer of the ocean that exists only in the
An invertebrate animal such as an insect, spider, or crab, deep trenches; some ocean trenches reach depths of 36,000
which has its skeleton on the outside of its body and has feet below the surface.
joints on its legs.
Fresh Water
Brackish
Water that is not the sea and does not contain salt. In nature a
Slightly salty, as is the mixture of river water and seawater in freshwater creature is not normally found in salt water, but as
estuaries. Brackish water is where freshwater and saltwater the Dungeon Master feel free to ignore this.
mix. These areas are filled with plants and animals that have
adapted to this “medium” level of salinity. Marine
Cephalopod Connected with the sea and the creatures and plants
that live there.
A mobile predatory mollusk found only in marine
environments. Midnight Zone
Cenote Any ocean depth below 3,000 feet is considered the
midnight zone, since no natural light from the surface
A deep, water-filled sinkhole in limestone, created when penetrates this deep.
the roof of an underground cavern collapses. This creates a
natural pool which is then filled with rain and water flowing Mollusk
from underground rivers.
Any creature with a soft body that is not divided into different
Civilization sections, usually with a hard outer shell.
For this work civilization specifically means any semi- Nautiloid
permanent or permanent collection of intelligent (usually)
humanoids that collectively live together. This is not the same For this work ammonoid and nautiloid are synonymous. Feel
as a creature’s lair. free to use ammonite, ammonoid, nautiloid, nautilus, or “weird
spiral thingy,” as you see fit. Note that some of these creatures
Continental Shelf come in straight configurations as opposed to the iconic spiral
that is normally associated with them.
Seabed around a large landmass that is relatively shallow
compared with the deep ocean. Ocean
The mass of salt water covering most of the earth’s surface.
“Sea” is interchangeable with “ocean.”
4
Reef Sunlight Zone
A ridge of jagged rock, coral, or sand just above or below the The sunlight zone extends from the water’s surface to a
surface of the sea. depth of 650 feet.
Salt Water Twilight Zone
Water containing salt, seawater. In nature a freshwater The twilight zone is between ocean depths of 650
creature is not normally found in saltwater, but as the and 3,000 feet.
Dungeon Master feel free to ignore this.
Underdark
Sea
A fictional setting that has appeared in Dungeons & Dragons
The mass of salt water covering most of the earth’s surface. role-playing campaigns and Dungeons & Dragons-based
“Sea” is interchangeable with “ocean.” fiction. This setting assumes most caverns and caves
are connected at some point. In this work, I assume that
there are lake, river, and ocean caves that also connect to
the Underdark.
5
CHAPTER 1:
UNDERWATER LOCATIONS
6 CHAPTER 1 | Underwater Locations
Lakes Water & Traps
Lakes can be pleasant places filled with nutritious fish, murky Adventurers can drown without ever having dipped a foot in a
areas hiding some ancient creature, or highly enchanted river, lake, or ocean. Outside of the obvious flooded dungeons
places filled with fey curiosities. Lakes can be relatively and ruins, you are highly encouraged to add water to traps
shallow or incredibly deep. Usually, an adventure involving and use rising water levels as a trap mechanism that threatens
a lake will not involve extended stays beneath the water but characters and forces them to make fast decisions. A trap
could easily involve a quick, magically-assisted dive to loot an with a rising water threat can be as simple as assigning a
aquatic monster’s lair. Because of this, underwater lakes are rate of rise that occurs at a specific Initiative count (usually
good locations for low-level underwater adventurers. Initiative 20).
Supernatural Lakes. Some lakes are entirely enchanted Flooded Pit Trap. Add three feet of water to a spiked 30-foot-
and considered magic locations with their own rules and deep pit, and it will have little to no impact. Add ten feet of
reality-warping mechanics. Some lakes hide undead and water to the same pit and a character might begin to panic if
other terrors that avoid the light, venturing out to wreak havoc they are not a good climber and are not rescued.
during nightfall. Lakes can also function as portals to different
realms and in one instance an entire lake is known to be an Truly Sinister Flooded Pit Trap. If you are feeling very
antisocial elder elemental of water (see Mordenkainen’s homicidal towards the characters, create a pit trap that is
Tome of Foes). pyramidal in shape. They fall through the top and land at
the base of the pyramid and if they climb the walls they are
Geothermals Waters. The natural world contains a wide inverted (increase the DC for Strength (Athletics) checks
variety of geothermal lakes, springs, and geysers. Some of to escape). Add enough frigid water to drown and cause
these are the rare warm oasis in an otherwise frigidly cold exhaustion, make the walls smooth as glass, and then put
environment, some spew toxic gasses that can kill instantly the entire area under an antimagic field, and well ... good luck
(refer to stinking cloud and cloudkill spells for game effects), finding new players!
and some are acidic or alkaline waters that normal life cannot
exist in. Regardless, they are almost always beautiful places Flooding Closed Room. The flooding room with locked
filled with bright vivid colors and will attract all sorts of doors is a classic trap trope. You can increase the difficulty of
creatures, monsters, and hermits. Some of these areas also these traps using frigid or boiling water, continuous lightning
link to deep superheated underwater caverns. damage, and many other devious ideas.
Rivers Drowning the Curious. If a dungeon or cave has a flooded
area, with easy access for a curious adventurer, chances are
Rivers tend to be the “highways’’ of medieval fantasy good that said adventurer will want to swim and explore it,
commerce and almost all of the large cities grow up around especially if something lures that adventurer to go further and
rivers large enough to transport ships to the coast or other deeper than is prudent. A simple lure is glowing treasure in
cities. Because of this, most rivers of any value will be clear water. At least one character has perished because they
somewhat tamed unless the adventurers travel deep into the gained two levels of exhaustion while swimming to the far
wilderness or to a frontier area. end of a flooded cavern, found a dry section with some loot,
and attempted to swim back before taking a Long Rest. This
Civilized Rivers. These rivers will tend to be polluted and “drowning the curious” room will usually only hinder your
double as sewers depending on how many humanoids are reckless or low-level parties without access to a clever druid
near them, but there is still plenty to explore. Adventurers or water breathing.
could be trying to exterminate some threat that lairs in the
river, deal with river pirates, or looking for hidden treasure Cave Exploration and Drowning. In the natural world,
and salvage. Rivers near an ocean or sea may even hide humans do find interesting ways to drown; some drown each
Gargantuan aquatic threats like the dragon turtle. year while exploring caves. In a fantasy setting characters that
get lost, injured, or otherwise stuck in a cave, might become
Wilderness Rivers. These rivers are great places to hide stuck in a low area that can flood and fill with water during
submerged or partially submerged ancient ruins and heavy rains. Those exploring caves with marine water access
dungeons as civilizations always tend to pop up around a river. run the risk of entering during low tide, and attempting to
Predators, even massive dragons, will also frequent rivers as leave during high tide, which can cause confusion or drowning
they are fertile hunting grounds. as the rising water tends to change the way the cave appears,
especially if the characters have been using multiple passages
Flooded Dungeons and chambers.
Your characters may have explored their fair share of Variant Rule: Tight Tunnels
dungeons and crypts, but how many of those locations Getting Stuck and Escape DCs
were completely submerged? A dungeon that is submerged
increases the threat to the characters, where simple mistakes Sometimes, rather tragically, a character gets stuck while
like letting water breathing expire could be deadly. Sunken trying to swim through a very tight flooded passage and is
ruins are less likely to have been previously explored but also unable to free themselves before they run out of breath. An
less likely to be inhabited by low challenge rating threats. easy game mechanic for this is to assign a grapple-like escape
DC at certain sections of an exceptionally tight or irregular
CHAPTER 1 | Underwater Locations 7
tunnel. Some of your characters will attempt to “push” Docks
through the tunnel, possibly facing harder escape DCs which
may or may not doom them, and some of them will back out Any moderately-populated surface civilization next to a river
and find a safer way through the tunnel or look for easier loot or large body of water will have a dock of some sort. This dock
elsewhere. Note that having a swim speed will not improve can be as simple as a long pile of rocks and dirt that extends
a creature’s chances of escaping getting stuck, but they will out long enough to reach a ship, or it can be a massive affair
live much longer if they can breathe water. A Small character of floating walkways, berths, and warehouses almost the size
should have advantage when making escape DCs against a of a town. Docks are the heart of legal and illegal commerce,
tight flooded passage that Medium characters can use. some of which ends up under the dock. For those equipped
and brave enough there is wealth and adventure to be had
Tunnel Escape DC 5. This tunnel is relatively easy to salvaging wrecks. The underwater section of the docks is also a
get through and shouldn’t give adventurers much trouble good place to start an underwater adventure, for the characters
other than the occasional annoyance. This tunnel is just are close enough to civilization and rescue that the threat of
wide enough for a crawling Medium character and the drowning is as low as it can be.
walls are smooth enough to not catch on the character or
their equipment. Diving Bells. Depending on the level of technology you allow
in your campaign, diving bells allow for some exploration of
Tunnel Escape DC 10. This tunnel is a tight fit that will worry the bottom of the docks with a device that looks like a large
most characters with a sense of self-preservation, especially bell that is used to capture air. The best diving bells also
if they are holding their breath. When a flooded tunnel gets have hoses attached to them that allow for the circulation of
to be this tight, most sane characters will back up and out breathable air.
of the tunnel.
Watery Graves. Docks are also a favored spot for disposing
Tunnel Escape 11-20. This tunnel is so tight or hard to of bodies, and certain criminal elements will surreptitiously
navigate that it can easily kill a stubborn character that is dump a corpse off of a dock in the hopes that it is never
holding their breath. This tunnel should even give a very discovered. This attracts natural and fantastic scavengers
nimble rogue some concern. and monsters, who might get impatient and start wandering
around the docks looking for fresher meat.
8 CHAPTER 1 | Underwater Locations
Sewers purposes, you don’t need to change most creatures if they are
encountered here unless you want to make aesthetic changes.
Adventurers eventually end up in the sewers; they just can’t seem Some aquatic civilizations can still be found at this level and
to help it. Sewers can hide large organizations like a thieves’ wandering adventurers and most aquatic humanoids must
guild and can also act as places for intelligent creatures and now protect themselves from crushing depth damage if you
monsters to hide from civilization. Sewers are sometimes secret use that variant rule.
escape routes out of castles and keeps. Every sewer system
you design should have at least a few areas that are completely Midnight Zone. Any depth below 3,000 feet is considered
submerged. Sewers also happen to be a great place to introduce the midnight zone since no natural light from the surface
new and interesting diseases (see Chapter 3). penetrates this deep. The midnight zone extends to a roughly
defined barrier with the abyssal zone at 13,000 feet. Natural
Oceans and Seas creatures are much rarer in this layer and have adapted to the
cold, lack of light, and crushing pressure in noticeable ways.
Zones Based on Depth This layer is inhospitable to any natural creature not native to
it, including aquatic humanoids without magical protection.
As you go deeper and deeper into the ocean, the creatures, Oxygen is so scarce here that a non-native aquatic or surface
available light, and environment change. The ocean has five humanoid that is breathing water must make a successful
large zones, with each zone being separated and defined by DC 10 Constitution saving throw every hour or gain one level
how far down (or deep) you are. of exhaustion.
Sunlight Zone. The sunlight zone extends from the water’s Abyssal Zone. The abyssal zone of the ocean is the layer
surface to a depth of 650 feet. This area of the sea has the from 13,000 feet deep to roughly 20,000 feet deep. In the
same natural illumination conditions as above the water. natural world, this layer of the ocean accounts for just over 80
Roughly 90 percent of natural marine creatures live in this percent of the ocean’s total volume. Most of the creatures in
thin layer of the ocean. Very few aquatic creatures, if any, have this zone live within 30 feet of the bottom of the ocean, eating
issues related to crushing depth damage in this layer. This marine snow and each other. There is a surprising amount
layer is where most of the aquatic civilizations call home and of diversity in the creatures found at the bottom of the ocean,
allows for relatively quick access to the surface for raiding, but creatures at this depth are so adapted that most, if not
trading, or exploration. all of them, will die if brought into a higher ocean zone. In a
fantasy setting, this is the zone with undead hordes and any
Twilight Zone. The twilight zone lies between the depths of number of sleeping or cosmic horrors. Oxygen is so scarce
650 and 3,000 feet. When the sunlight zone above is bathed here that a non-native humanoid must make a successful DC
in natural bright light, the twilight zone is filled with dim 15 Constitution saving throw every hour or gain one level
light. If the sunlight zone is filled with dim light or darkness, of exhaustion.
the twilight zone is dark. Most natural aquatic creatures
will avoid this zone due to steadily increasing pressures Hadal Zone. The hadal zone is the layer of the ocean that
and a slowly decreasing level of available oxygen. For game exists only in the deep trenches; some ocean trenches reach
depths of 36,000 feet below the surface. Life at this depth
CHAPTER 1 | Underwater Locations 9
will be very, very strange. As the Dungeon Master, feel free to Bone Muck. In a fantasy setting, ocean muck lying at a depth
create whatever odd thing you want at this depth. The deep- of 650 feet or more can sometimes concentrate necrotic
water snail is an example of such a creature; it was specifically energy, and these sections of bone muck can be up to
designed for this layer, and can be found in Chapter 7. There is hundreds of feet across. Bone muck causes 1 necrotic damage
no oxygen to be had here, regardless of water breathing or airy to any living creature within 5 feet of it or 1d8 necrotic damage
water. Explorers will have to bring or create their own oxygen to a living creature if it starts its turn touching the muck. Bone
supply at this depth. The new spell, utility, can be used at this muck looks exactly like normal muck unless there is a light
depth and it is explained in Chapter 6. source nearby. Any light that gets within 30 feet of bone muck
will begin to flicker and dim. Bone muck also acts as a magnet
Sea Floor for the undead hordes that roam the bottom of the ocean.
The floor of the ocean can hold or hide anything you can Shipwrecks
imagine, from ancient cities, kuo-toan temples, ancient
horrors, Colossal creatures (see Chapter 7) and their lairs, Many, if not all, underwater adventurers of any size and
and any imaginable treasure or secret. duration have at least one shipwreck to explore. The
shipwreck section of Ghosts of Saltmarsh has been expanded
Blue Holes. Blue holes were introduced in Ghosts of below so that you can randomly determine the size of the ship,
Saltmarsh and are circular sinkholes found in shallow what is guarding it, or lairing in it, and what sort of treasure
water. The dark blue of the hole sharply contrasts with the can be expected.
lighter blue-greens of the shallows. Blue holes will attract
adventurers as well as creatures, and often contain submerged Shipwreck Type
caves and passages at their lowest sections. Due to the lack of
water circulation, some of these will also contain large dead d100 Description
zones with little to no oxygen. 01-05
Multiple ships were sunk at the same time or place, usually
Marine Snow. This is organic material slowly falling from the 06-10 due to a naval battle or another potent ocean catastrophe.
upper layers of the ocean to the ocean’s floor. This material, 11-20 There are 2d12 total ships, each with its own guardians
usually bits and pieces of animal bodies, can sometimes take 21-30 and treasures, or with something powerful guarding the
weeks to fall to the bottom of the ocean, where an amazing 31-42 entire site.
diversity of creatures survive just by eating the marine snow. 43-73
74-84 Barge
Muck. Much of the ocean floor is covered in a combination 85-99
of slime, sediment, and slowly decaying organic matter often 100 Rowboat
referred to as ocean muck. This muck can sometimes be as
thick as 10 feet and most Tiny or Small creatures can walk Keelboat
on it with little difficulty. Medium creatures without a swim
speed treat muck as difficult terrain. Those disturbing this Longship
muck create a 10-foot-radius sphere of heavily obscured water,
but the material is usually not dangerous and easily escaped Sailing Ship
unless a creature is immobilized and buried in the muck.
Galley
Warship
Very Strange (this can be from any other source you have
access to, from the Spelljammer Campaign Setting, the
Planescape Campaign Setting, homebrew, other third-party
resources, or something completely out of place at the
bottom of the ocean like an inn or wagon).
10 CHAPTER 1 | Underwater Locations
Shipwreck Guardians backpack. An underwater civilization will have different “fruits
and vegetables” than a surfacer is used to, and they may be
d100 Description completely unrecognizable.
1-10 Nothing dangerous
11-15 1 eye of the deep Food (Unrealistic). If realism is not that important in your
16-25 1d12 oozes or slimes campaign, then you do not need to change much for food.
26-30 1 marid An underwater civilization has easy access to air filled areas
31-40 1d4 mertraps and 1d6 giant clams where they can brew and cook surface foods, or you can
41-55 2d4 giant crabs ignore the “how” completely. This is by far the easiest way to
56-70 2d12 reef sharks handle underwater civilizations and food.
71-72 1 dragon with a swimming speed
73-81 1d4 giant sharks Air Pockets
82-86 1d4 scrags
87-90 1 colossal octopus Almost every aquatic civilization and some lairing creatures
91-98 Natural hazard (see Chapter 3) will find or create a few air-filled spaces. These spaces are
99-100 Supernatural hazard (see Chapter 3) used for temporary visitors, combat practice for future surface
raids, keeping of prisoners, metalworking, storage of valuable
Use the following table with Chapter 8 of the Dungeon objects that rust in salt water, brewing, etc.
Master’s Guide.
Natural Air Zones. Natural air zones can be created by natural
Shipwreck Treasure means, but the oxygen levels will be hard to replenish unless
it is piped in somehow, or created naturally. These zones can
d100 Description be inhabited by air breathers, but only for a short time before
01-05 Nothing the oxygen level becomes depleted and they begin to suffocate.
06-35 CR 0-4 (individual treasure) Forging and alchemy are usually impossible in an area like this.
36-50 CR 5-10 (individual treasure)
51-59 CR 11-16 (individual treasure) Magic Air Zones. Magical air zones are created by spells,
magic items, supernatural creatures, artifacts, or portals to the
60 CR 17+ (individual treasure) Elemental Plane of Air. Any such zone that does not need to be
61-71 CR 0-4 (treasure hoard) constantly charged with oxygen is incredibly valuable and allows
72-80 CR 5-10 (treasure hoard) for forging, alchemy, permanent air-breathing, etc. Civilizations
81-85 CR 11-16 (treasure hoard) with access to the new spell utility (see Chapter 6) will usually
use this spell as a means of maintaining a few magic air zones.
86 CR 17+ (treasure hoard)
87-95 Roll twice, ignoring any duplicates of this result Civilized Places by Race
96-100 Roll three times, ignoring any duplicates of this result
Aquatic Humanoids. Aquatic civilizations are different from
Civilization lairs; firstly, in that the “encountered” group does not live
Beneath the Waves in the same place and secondly, that most of them are not
directly related to each other.
Realism
Aboleth (500-5,000 feet). Aboleth civilization will include far
You should decide early on whether realism matters to you more slaves than aboleths, chuuls, and skum.
and your players, and if so, to what degree. Realism can be a
tricky thing to implement in a fantasy game with magic and Aldani (0-50 feet). These creatures are usually lake and river
monsters, but the right mix for you and your players can make dwellers. Civilized places for this species could be as large
all the difference between a decent campaign and one in which as a village.
the players are totally absorbed. Your decisions about realism
will have the largest impact on how the characters interact with Bullywug (0-100 feet). These creatures will often have
underwater civilizations. Simple things like eating, drinking, dwellings that are both above and below the surface. Civilized
sleeping, materials, and the storage of knowledge can either places for this species could be as large as a town.
be glossed over, or you can spend days figuring out if and how
underwater civilizations manage these tasks. We will tackle Cosmopolitan (0-200 feet). Cosmopolitan means that the
food as an example of different levels of realism. civilization has a wide variety of humanoids and creatures
that have found a way to not murder each other or otherwise
Food (Realistic). If your campaign needs to be very realistic, fragment and die out. Civilized cosmopolitan places could be
then an underwater civilization will eat almost everything raw, as large as the largest surface city.
or possibly boiled if they have access to hydrothermal vents.
A triton may bring a living creature as a snack or kill and Grung (0-100 feet). These creatures are usually swamp or
eat something as it travels, as opposed to having rations in a marsh dwellers, but parts of their homes could be partially or
completely submerged. Civilized places for this species could
be as large as a village.
Ixitxachitl (0-500 feet). These creatures are incredibly
chaotic and the closest they come to participating in
civilization are semi-permanent spawning areas that could be
as large as a village.
CHAPTER 1 | Underwater Locations 11
Koalinth (0-500 feet). These creatures will want to be near treasure and sacrificial victims. They will even attack weaker
the surface so they can raid it for plunder or murder. Civilized evil neighbors. They will likely control areas that allow for air-
places for this species could be as large as a town. breathers so that they can keep a few on hand for sacrifices.
Sahuagin civilized places can reach the size of large towns.
Kuo-Toa (100-1,000 feet). These creatures are arrogant enough
to think they own the entire ocean and will place their living Sea Elves (0-300 feet). These elves split from surface elves
areas wherever they are not immediately fought or destroyed. long ago but still maintain limited and good contact with
Civilized places for this species could be as large as a city. surface elves.
Lizardfolk (0-50 feet). These creatures will have parts of their Tortle (0-100 feet). These creatures are very nomadic but
civilization below the surface, but most of it will be on the when they do settle down it tends to be in small groups no
surface as they are not truly amphibious. Civilized places for larger than a village.
this species could be as large as a town.
Triton (10-600 feet). These creatures tend to be more close-
Locathah (10-1,000 feet). These creatures will tend to lair near minded when it comes to contact with surfacers and will
other neutral or good-aligned aquatic humanoids and are the be less likely to be inviting towards unexpected guests or
most likely to be “neighborly,” if unexpected adventurers show adventurers. They will have a handful of cities that rival the
up. Civilized places for this species could be as large as a town. size and scope of what is found on the surface.
Marid (100-50,000 feet). These elementals are completely at Flooded Caves
home in the water and can lair at any depth imaginable. If they
have a civilized place larger than a village it will be deeper Underdark Access. Some underwater caves and caverns
than 3,000 feet where they can expect to be left alone. link up with the Underdark and they either lead to air-filled
passages or open into the bottom of underground lakes and
Merfolk (10-200 feet). These creatures tend to remain in rivers. Due to the immense pressure of the ocean, the currents
shallower sections of the ocean and use the sun to tell the time almost always flow into the Underdark. Some of these areas
and the seasons. This civilization is usually nomadic but could where the ocean meets the Underdark are known to both
have permanent settlements as large as a city. aquatic and Underdark civilizations.
Merrow (10-600 feet). These creatures are equal opportunity Saltwater Caves. These underground caves are filled with
tormentors who will hunt or fight surface creatures as well as salt water and support a wide variety of life or are used as the
aquatic humanoids. lairs of underwater creatures. These may or may not have
openings to the surface. The deeper you go beneath the ocean,
Sahuagin (300-1,500 feet). These creatures will sometimes especially after 1000 feet, you will find far fewer to no caves at
attack surface ships out of simple bloodlust or in search of
12 CHAPTER 1 | Underwater Locations
all. Some deeper saltwater caves will have little to no oxygen Wonder and Inspiration
in them and these caves will be avoided by most life.
Wonder can be found in any source that you wish to pull from.
Brackish Caves. These caves mix salt and fresh water and The natural world is also filled with incredibly amazing things,
the water is a unique mix of the two that supports its own from salt icicles under the polar caps, methane hydrates,
form of life. Creatures native to brackish waters may or may translucent animals, etc. When in doubt, ask the rock gnome
not be able to survive in fresh or salt water for a length of twins, Siri and Google. It is always best to have a few of these
time. Where salt and fresh water mix there tend to be side standing by for when you want to lighten the mood or if your
caverns and “cut-aways” due to chemical processes that eat players are clearly done with fighting or doing anything serious
at the walls. during your session.
Freshwater Caves. Freshwater caves are normally found Dome Kelp. Dome kelp is a special type of kelp bred by merfolk
underground with no access to underground saltwater areas. and sea elves, but it can also be rarely found in the wild. Dome
In some instances, there is a very unique and distinct line kelp magically produces air bubbles along its main stalk that
where two types of water meet, like in a cenote. slowly break off and float to the surface. These bubbles can be
trapped with any kind of dome and eventually a breathable area
Underwater Wonder will form. It takes 100 plants to create a dome of air roughly 10
feet in radius. This dome of air can only support one Medium
Sights air-breathing creature indefinitely, for the plants cannot replace
the oxygen very quickly.
Bright Colors. Underwater environments can be a
kaleidoscope of vibrant colors of every imaginable shade. Extruder Rope. Extruder rope is a magical marine slug that
Remember to describe these colors when relevant. This can rarely be found in the wild, but is often kept in herds by
will be true for most locations that are not in the twilight or aquatic humanoids. This slug will slowly sift and eat sand,
midnight zones of the ocean. dirt, and marine snow at the bottom of the ocean, extruding a
quickly hardening rock (very much like concrete). If the creatures
Deep Darkness. Underwater environments can also be are well fed and tended to by a knowledgeable creature, then
pitch black, a darkness so complete that there is no ambient roughly 10 extruder ropes could make a 5-foot-wide, 5-foot-tall,
light. Even Darkvision may only show a field of grey if 1-foot-thick wall in a month that would look like a single piece
there is nothing within range. In such an environment the of irregular rock. Some of the aquatic races will feed the slugs
smallest amount of light will be striking. This darkness a specific diet to change the colors of the rock that is extruded.
can be encountered in an underground cave with no Without dye the extruded rock is a pale beige.
phosphorescence or bioluminescent creatures. This type of
darkness can also be encountered in the midnight or deeper Sand Eaters. Sand eaters are distantly related to extruder
zones of the ocean. rope marine slugs and are hard to tell apart until they start
extruding. The sand eater extrudes rock that is translucent
Sounds or transparent if its diet is strictly controlled. Sand eaters are
harder to breed and keep alive, and worth roughly 100 times
Whale Song. The oceans can be utterly silent at times. Other as much as an extruder rope.
times the ocean is filled with the strange songs of whales or
the clicks of dolphins. In a fantasy setting, there can be other Chromatic Bubbler. These freshwater arthropods, no larger
noises, like a bustling merfolk town or eldritch chanting rising than a flea, wander the bottoms of lakes and ponds, quickly
from the abyssal zone. Whales and natural creatures born emitting a chromatic bubble around itself if it feels threatened.
to the water do not lose breath when using echolocation or This bubble is magically hardened and will not pop until
making “whale” songs because they do not exhale like surface it floats to the surface. Most creatures have learned not to
creatures that wish to talk, growl, or scream. swallow one of these due to how painful that can be. These
bubbles, for the most part, are just an aesthetic wonder, having
Creatures no impact on gameplay. The bubble is completely immune to
nonmagical damage and a chromatic bubbler can only form a
Babble Fish. The babble fish is a legendary magical fish that bubble once every two hours.
is difficult to tell apart from their natural counterparts without
detect magic or other means. This valuable fish produces a Wonder for Wonder’s Sake. The natural ocean is filled with
magical 20-foot-radius sphere effect, centered on itself, that wonder. While running an ocean campaign, find time to add
allows all creatures to understand each other so long as a simple encounter with no combat, role-playing, negotiation,
they are underwater and can hear each other. These fish are or moral dilemmas. Just describe something wondrous. The
so rare and valuable that they are guarded like royal jewels random encounter labeled, “Wonderfall,” in Chapter 2 is a
or precious artifacts. A babble fish will live for roughly 40 good example of this.
years before dying. They will breed with other babble fish or
nonmagical specimens but only 1 in 1,000 of their children
will also be babble fish. A babble fish will otherwise behave
(and have the statistics) of a natural fish of its type and size.
CHAPTER 1 | Underwater Locations 13
Unique Underwater that succeed on this saving throw have one turn to act in
Locations whatever way they wish as they slowly fall towards the portal
leading to the infinity source. At the beginning of each of their
Max next turns, while passing through Max they must make a
successful DC 21 Charisma saving throw or be plane shifted
This unique location can quickly kill irrational or violent to anywhere that the DM chooses.
characters that are not level 17 or higher. But if a character
happens to be Huge or larger then they will be in grave danger Max is not a creature in the conventional sense. Anything
regardless of their temperament. Max can either be brand “passing through” cannot harm Max unless someone finds
new, and its sudden existence creates grave concern for local a way to bring an extra-dimensional object or effect into this
leaders, or Max’s maw and source could have been in the area area, in which case Max is annihilated and everything inside
for hundreds of years, creating very dangerous currents in one it is randomly and violently thrown throughout the multiverse.
location and slowly building islands in another. This violent destruction should be able to kill anything under
Max is both an extra-dimensional creature and place. Max’s CR 21 currently inside Max, but how that occurs is up to the
“body” exists in a demi-plane, fed by it’s bottomless maw. As Dungeon Master.
material passes through Max from the bottomless maw it exits
back into the Material Plane via the infinity source. Max can Passing through for Huge and Larger Creatures. Huge and
choose to change where its bottomless maw or infinity source larger creatures that pass through the bottomless maw will
is located on a Material Plane. find themselves suspended in a 3-mile diameter stomach of
searing acid, taking 22 (4d10) acid damage at the end of each
Bottomless Maw. There is only one bottomless maw, and of their turns. Creatures that breathe, regardless if they need
it is the mouth (one-way portal to Max) of an eldritch extra- air or water, cannot breathe this acid. Anything not destroyed
dimensional creature described as a living demi-plane. This after 10 minutes of acid damage will be plane shifted to
creature, which some fool named Max, will occasionally open Passing Through unless they make a DC 21 Charisma saving
a 30-foot diameter portal at the bottom of an ocean crater for throw. Max will then focus its eldritch intelligence on the
a few hours. When the portal is open (when Max is feeding), creature and begin a telepathic conversation. A creature that
a strong current is created as the creature starts drinking can survive the acid and make a saving throw against the
the ocean. The speed of this current is 60 feet towards the plane shift can damage max if they get close to the stomach
center of the crater. The crater, or maw, is a rough 120-foot- wall. The wall has 14 AC, is immune to acid, cold, thunder,
diameter crater in the ocean, about 600 feet below the and bludgeoning damage. Each 5-foot cube of wall has 80
surface. Inorganic material and water travel through the maw Hit Points but the stomach is 120 feet thick. Any creature
unharmed. Large and smaller creatures are usually ignored damaging the stomach wall is targeted with a DC 23 9th-spell
as they pass through the creature unless they become violent. level disintegrate once regardless of how long they remain in
Huge and larger creatures end up in the acid stomach (see the stomach. If the creature is still alive then Max will begin
Passing Through). to beg for its life for if the stomach wall is breached Max dies
The bottomless maw has truesight 180 ft. and if it detects an exactly the same as if an extra dimensional space entered
interdimensional space like a bag of holding or equivalent Passing Through.
magic the portal will immediately shut down and not reopen
until the threat is removed. If the threat is not removed Infinity Source. The infinity source can be located up to 20
then Max will open a new bottomless maw elsewhere when miles away from the bottomless maw and is exactly what
Max becomes hungry. The old crater will then slowly fill in most creatures say it is in impolite company. It is literally
over decades. the “exit hole” of a strange extra-dimensional creature. The
infinity source is sometimes referred to as the “god-ass.” The
Passing Through for Large and Smaller Creatures. Any infinity source is an unadorned section of the sky that opens
creature passing through the bottomless maw (portal) up when Max is feeding and anything that passes through
will enter Max’s demiplane body and likely survive unless it falls from this location in the sky. While open, everything
they become violent. While passing through Max, organic passing through (see above) exits Max from an invisible portal
creatures describe a psychedelic experience of sounds and 60 feet above a large lake or ocean, usually within easy sight
colors that can’t be explained and a feeling like falling. All of a coastline. If Max is being lazy and not moving the infinity
material that enters from the bottomless maw is slowed source, then the falling debris eventually creates an island and
down and separated while passing through Max and nothing when the island gets within 30 feet of the portal Max will shift
collides during this orderly and oddly tidy passage. A creature the infinity source 120 feet in any direction. If Max has been
will experience one minute of time, and if they attempt to do active in a particular world for a while there may be many
anything violent, cast spells, or otherwise interfere with the small artificial islands created over time.
orderly passage of things around them then Max will attempt
to crush them with a psychic attack designed to pacify them. The Odd Path (The Odd Network)
A creature targeted by Max with a psychic attack must make
a successful DC 18 Intelligence saving throw or be paralyzed These unique portals can be used as fast transportation
until they exit Max through the infinity source. Creatures between ocean sites for those who know how to use them. No
one remembers the name of the demigod that was torn apart in
ages past, but all that remains of it are its massive heart, veins,
and arteries that defy the rules of space and time. This massive
14 CHAPTER 1 | Underwater Locations
CHAPTER 1 | Underwater Locations 15
circulatory system consists of a central heart roughly 400 feet Plane of Air, but these “drains” tend to be no larger than a
in diameter hidden somewhere deep in the earth and at least Small creature.
fifteen entry and exit portals that allow passage to and from the
heart chamber. Those who have discovered this unique means Earth. A portal to the Elemental Plane of Earth is usually
of travel refer to the long-dead demigod as “Odd,” and the marked by an unnatural amount of bubbling and churning
system is usually called “the Odd Path,” or “the Odd Network.” mud. These portals tend to be oddly stable, allowing creatures
to pass through while only allowing a minimal amount of
Odd’s Heart. No living creature knows where this massive earth or water to pass back and forth.
chamber exists but it functions as the central hub for the Odd
Path network The chamber is an irregular-shaped granite Fire. Portals to the Elemental Plane of Fire are usually found
void roughly 400 feet in diameter. The chamber is further in underwater volcanoes, hydrothermal vents, or trenches.
separated into eight sections, separated by walls of red granite Telling a natural vent of magma and superheated steam apart
usually 30 feet thick. Six of the chambers have salt water from a portal is usually very difficult (DC 15 to 20 Intelligence
basins about 40 feet deep. Within these wet chambers are a (Arcana) check) as they look so similar.
multitude of tunnel openings 10 feet in diameter with ramps
leading out of the water and then to platforms that join the Water. These portals can be dangerous as they can float
different heart chambers. Each tunnel is submerged and if invisibly at any depth, and creatures may pass through them
traveled through, they end in a magical portal after 3d100 feet. unknowingly unless aided by magical sight, such as truesight,
The air in these chambers can never be fouled or replaced by or specific spells designed to detect and locate portals to other
any other gas (no natural or magical effects that use gas or planes of existence.
remove oxygen will function here).
Water and the Outer Planes
Odd Portals. Each portal is one way and either allows
creatures to enter the Odd Path, eventually leading to one of Large bodies of water and sometimes other liquids, such
the six wet chambers, or leads out to an ocean location. as acid and blood, can be found in the Outer Planes. The
following list of large bodies of water is not exhaustive but they
Each exit portal irises open when in use and then are the most well-known.
immediately closes after a creature passes through it. No
known means can force a portal open or force it to reverse Abyssian Ocean. This strange bottomless ocean is
how it functions. Exit portals will deposit a traveler at an sometimes called the Soulless Sea and can be traveled to or
ocean depth, 4d10 x 100 feet deep. from any water in the Outer Planes. Those who end up here
are usually lost or arrive by accident. Although it exists in the
Each entry portal is obvious from the ocean and looks Abyss, this ocean’s demonic denizens are strange and almost
like a slowly beating red fleshy mass on the ocean bottom. unheard of in the Prime Material. No demon lord claims
This mass will be between 5 and 10 feet wide. Any creature dominion of the Soulless Sea; instead, strange aquatic demon
touching the mass must make a successful DC 20 Charisma warlords called the myrmyxicuses rule here, each having
saving throw or be pulled through instantly into a tunnel absolute power over large sections of the Abyssian Ocean.
leading to one of the wet chambers. Entry portals can be
found at any ocean depth below 200 feet. Styx. Arguably the most famous river in the Multiverse, the
River Styx is a dangerous river that connects all of the Lower
Dry Chambers. Depending on your needs, the two dry Planes but completely drains a creature’s memory and/or
chambers are empty or possibly filled with some sort of sanity. Merrenoloths will sometimes take travelers along the
small town of humanoids or creatures that run businesses River Styx for a price.
or otherwise act as a high magic/high fantasy town. These
dry chambers can also hide ancient horrors or anything Oceanus. This river is best described as a calm and
else you desire. pleasant version of the river Styx that connects most of the
Upper Planes.
Water and Other Planes
Others.
Elemental Portals
Abyss. Layers 13 “Blood Tor”, 88 “Gaping Maw”, 89
Large bodies of water, especially seas and oceans, have “Shadowsea”, 480 “Guttlevetch”, 493 “Steeping Isles”, 499
many portals to the Elemental Planes. Most portals found “Carroristo”, 531 “Vudra”, and 570 “Shendilavri” all have, or
underwater, except ones for Elemental Water, tend to be are, large bodies of water or other liquids.
obvious and hard to stumble into blindly. Elementals usually
congregate around portals, especially if the portal is two-way. Arborea. Layer 2 “Aquallor” is an endless emerald ocean.
Air. A portal to the Elemental Plane of Air would resemble a Carceri. Layer 5 “Porphatys” is a shallow acidic ocean with
bubble or a drain, depending on how the portal is operating. A black acidic snow and the occasional rocky island.
bubble would allow surface creatures to exist below the surface
so long as the portal did not close. The eventual diameter of this Elysium. Layer 4 “Thalasia” is the beginning and the end of
sphere of air created by such a portal is up to you, but anything the river Oceanus and is itself an immense ocean with a wide
inside this bubble would also be safe from damage caused by variety of small islands.
depth. A drain would then be a one-way portal into the Elemental
Nine Hells. Layer 5 “Stygia” is a dark ocean of cold mist and
mountains of ice.
Seven Heavens. Layer 1 “Lunia” is an infinite beach next to
the Silver Sea -- an infinite ocean of holy water.
16 CHAPTER 1 | Underwater Locations
CHAPTER 1 | Underwater Locations 17
CHAPTER 2:
UNDERWATER CAMPAIGNS
18 CHAPTER 2 | Underwater CAMPAIGNS
Lure Mix Fantastic and Real. Underwater campaigns should both
be familiar and alien to your players and their characters. If
Adventurers are not your average humanoid. They you mix what is found in reality with truly fantastic things like
either sought out danger, excitement, and loot or had the colossal creatures (guidelines for colossal creatures are found
adventurer’s life thrust upon them. A commoner fishing off in Chapter 7), forgotten evils, mythic civilizations, etc., then
a pier may wonder what lies at the bottom of the ocean, but you will create something truly memorable. This work will
it takes an adventurer to want to go there and experience it show constant examples of the fantastic and the real.
… and hopefully live through the experience. Adventuring
underwater is usually something only the experienced Aquatic Adventurers. Adventurers that can breathe water or
adventurer can manage safely. You can create survivable hold their breath for an extended period would obviously have
scenarios where level 1 characters explore under the water, an easier time with an underwater adventure. If you allow this
but you must be careful, for a campaign under the waves it is best to give all of the characters this advantage or find
can go wrong rather quickly, especially if your players are some other way to counterbalance a water breathing character
impulsive or refuse to keep track of a water breathing spell with fellow companions that cannot.
duration and the passage of time.
Necessity. If you want the adventurers to explore underwater,
Underwater Wonder or Underwater Danger. Decide early and normal motivations don’t seem to be working, then place
on if you want water to be just a setting or if you want water to whatever widget, object, MacGuffin, or lore they need at the
be an ever-present threat. If you give all the characters rings bottom of the sea and they will find a way to get to it.
of water breathing, then water will mostly be just a setting
they can explore at their leisure until they stumble across an
antimagic field. If the characters must ration spell slots or
potions of water breathing, then the water will be a constant
threat that they will have to account for or drown in if their
magic runs out. Each of these options has pros and cons, with
one favoring a leisurely but strange stroll through wonder,
and one of them leading to well thought-out plans with
(hopefully) a few back ups to prevent drowning. That being
said, high-level characters will have a wide variety of methods
to avoid drowning.
CHAPTER 2 | Underwater CAMPAIGNS 19
Resources Drive Ambergris. This dark grey waxy and flammable substance
Conflict, Conflict is sometimes referred to as “whale vomit.” Sperm whales
Drives Adventure secrete the substance in their guts and either pass or vomit it
up, where it floats and sometimes makes its way to a beach.
Conflict can create adventure or force the characters to explore Perfumers keep this substance in extremely high demand
the depths. The causes of a conflict can be simple, such as and on average it is worth 1 gp per ounce. Most chunks of
competition for resources, misunderstanding between surface ambergris are just a few pounds but large lumps of up to 100
and underwater inhabitants, ideological reasons, etc. Or the pounds can be found occasionally.
causes of conflict can be unclear and create situations of moral
ambiguity where one side is not the obvious “good” or “evil” Precious Gems and Jewelry. The oceans also provide
choice. A good example of this is when a coastal city is slowly mother-of-pearl, pearls, sea shells, ivory, and jewelry-grade
polluting a river and ocean as it grows. This damage slowly coral, etc., that all have value either directly to an adventurer
destroys the environment and threatens a previously unknown or to those who may need to hire some.
aquatic civilization. The city can only stop polluting if it is
abandoned. The aquatic civilization may have already moved Abalone. Abalone refers to the marine kelp snail, its shell,
once to avoid pollution, and for whatever reason, will not (or as well as the organic gemstone made from its iridescent
simply cannot) move again. shell. This ambiguity can create problems so for this
work abalone refers to the cut and polished shell that has
Natural Resources already been worked into jewelry. Abalone “stones” come
in iridescent greens, blues, and purples, and are used in
Agriculture. Kingdoms thrive on their peasants which run ornamental jewelry.
the farms which depend on water. Any attack on this chain is
a direct and immediate threat to power. Some civilizations Irregular Pearls. Irregular pearls are pearls that are not gem-
collapse if they cannot fish or extract food from the quality. These can be almost any imaginable shape and size
rivers and oceans. and are considered the standard “coin” of the aquatic humanoid
races. Irregular pearls are assigned values based on their
Clean Drinking Water. This is, without a doubt, the most weight and/or volume depending on who is trading them.
important resource for any living creature for without it there
is no natural life. In areas where clean drinking water is Gem-Quality Pearls. These pearls are usually spherical,
scarce conflicts can easily arise over water rights or anything uniform in color, and have a high-quality luster. A pearl
that threatens clean water. of this quality is usually worth more than a handful of
irregular pearls.
Water Work. Flowing water can also do work, as is the case
with a water wheel or water-driven mills. If the water stops Jewelry-Quality Coral. This coral is usually a deep red or
flowing, then everything that depends on flowing water to uniform pink color and is kept as-is, or cut into a pleasing
produce work simply stops. shape. As the Dungeon Master, feel free to come up with non-
natural colors of jewelry-quality coral, such as amethyst or
Creatures. Most creatures taken from the water can be eaten. emerald shades.
Some also provide fur, blubber, oil, bones, and other resources
that can be used or traded. Anything threatening a particularly Larimar. Larimar is an exceedingly rare gemstone that is only
abundant or sought-after resource will motivate the powerful found in marine rock formations. The gemstone produces very
to seek out adventurers if their normal means of security fail. If vivid blues and whites that can sometimes look like bubbles
your campaign dabbles in the steampunk genre, for example, and scales depending on how it is cut and polished.
then refined whale oil’s use and harvesting can easily create
conflict or tension, or this oil can be used as a means to explore Salt and Sand. Salt can be extracted from ocean water by
a wide variety of ecological issues and impacts. evaporation, and even some inland salt lakes are used to produce
salt. Sand is also an often-underappreciated resource for
construction that is extracted from some rivers and the ocean.
Seaweed. Edible seaweed has long been a staple of coastal
communities. Vast farms of the stuff can be farmed with little
to no technical skills or tools.
Fire Ice. Fire ice (methane hydrate) occurs naturally in ocean
sediment that is under at least 500 feet of water. This ice is
easy to identify because it is opaque and milky white, and is
either found at the bottom of the ocean or just beneath the
sediment. These chunks of fire ice can be small or massive,
and if brought to the surface they will burn if ignited. Fire ice
will slowly evaporate if brought above the 500-foot depth line
or to the surface, but it is useful as either a strange, naturally
occurring oddity or can be used in your campaign as a special
type of fuel or component in alchemy. Underwater civilizations
can also use this to start fires or augment forging in air-filled
rooms, but storing it is near impossible unless it is kept at high
pressures or in very (magically) cold containers.
20 CHAPTER 2 | Underwater CAMPAIGNS
Fantasy Resources Civilization
Above the Waves
Creatures. Civilizations can harvest giant aquatic creatures
like crabs or fish for food and other resources, and even Civilization, especially in a fantasy setting where magic is not
the corpses of the monstrous or weird have great value to
spellcasters and alchemists. ubiquitous, requires water to function at all. Goods, people,
Precious Gems and Jewelry. Anything valuable in a natural armies, raw materials -- almost everything -- travels on the
setting is usually still valuable in a fantastic one and, as a
bonus, natural resources can be found in fantasy settings rivers and seas, or civilization does not exist. Flowing water is
with impossible colors or sizes, from radiant pearls to pearls
the size of grapefruit. If, for example, your campaign needs a often used to produce work in the form of water wheels turning
shadowy soft substance for use in magical items then design a
supernatural underwater area that produces the stuff, which is a mill or floating lumber down a river instead of hauling it with
hard to locate or exploit.
wagons. Rivers, lakes, and the sea also provide food directly
Radiant Pearl. These pearls emit a very bright white light, but
only if they are submerged in brackish water or saltwater. If to larger urban populations and function as a convenient place
exposed to air or freshwater they look like dull grey rocks. Their
value is based on their size and brightness. Unlike most pearls, to dispose of waste. There is unlimited adventure potential
their shape is usually irrelevant. The most valuable radiant pearls
shed bright natural light in a 30-foot radius and dim light out to associated with civilization’s dependence on water. The
another 30 feet. Radiant pearls are found in flat black oysters.
following hooks are great places to start building a campaign
Shadow Coral. This dark purple coral has the same
hardness and characteristics as bronze. Shadow coral that around water.
is not enchanted or protected will quickly disintegrate if not
submerged in water, with most pieces crumbling away after Civilization Underwater Adventure Hooks
a few hours. Shadow coral is all that remains when a blinder
vile disintegrates. d10 Inspiration
Sea Glass. Most of the aquatic humanoids know how to coax 1 Something underwater is preventing the movement of soldiers
a variety of sea slugs called sand-eaters into slowly making a and supplies and it must be defeated, destroyed, or negotiated
type of pale glass that is transparent in saltwater and completely with before the local rulers can wage war with a neighbor or
opaque in freshwater or if exposed to air. Sea glass comes in survive an upcoming conflict with one.
a variety of densities, thicknesses, and color tints, based on
which sea slug is being used to make it. Sea glass, once made, 2 An important person or creature is being held captive by
cannot be melted down and recast into a new shape, so the amphibious or aquatic humanoids that are using their captive
skilled artisans who work with it tend to be incredibly patient and to leverage someone important to either pay them a ransom,
exacting. A single sand eater can only generate roughly a pound return a resource, or leave them alone completely.
of sea glass in an entire year, and an expert crafter may have
herds of dozens or hundreds of them in special grottos. Sea glass 3 A resource, important to local rulers for wealth or political
made by the locathah is generally considered the best quality. power, is under threat of either natural or supernatural
destruction and the adventurers are hired to prevent it.
Seawater Technology. Feel free to take a modern invention
and place it in your campaign: alter its technology to use 4 A magic item that the characters wanted to purchase or find
magical means. A gnome alchemist may have found a way was on its way to the seller when the ship sank. The seller
to desalinate large quantities of sea water or use it in an apologizes and will give the characters the location of the
alchemical battery. wreck if they promise to return half of the wealth and items
found in the wreck.
Sugar Weed. Sugar weed is a type of seaweed that grows
beets the shape and color of an orange, which can be 5 A local religious or cult leader has predicted that a tsunami
harvested like sugar beets. Certain chefs and coastal will soon destroy a coastal town or city. The characters are
communities prefer the taste of sugar weed to more familiar either hired to make the speaker recant their predictions
sugar sources like sugar cane. Aquatic civilizations will also and/or disappear, or to find a way to avoid the imminent
harvest and guard large patches of sugar weed. catastrophe.
Planar Portals. The oceans, lakes, and some ponds, are home to 6 A village near the capital has been reporting a strange low
a wide variety of stable portals to other planes of existence. Some hum coming from their well for months. The adventurers
can only be turned on with keys, open only during certain times are sent to investigate and soon learn that the very deep well
and events, or very rarely remain permanently open. The deepest broke into a vast underground lake.
points in the ocean are the only known two-way permanent
portals to Carceri. Stable portals are often valuable to those who 7 Every seven years a coastal city is hit with a tsunami. This has
know how to exploit them or those powerful enough to survive been going on for decades and the adventurers are hired to
travel outside of the Material Plane. either protect the city or stop the tsunami from hitting this
year.
8 An adventurer’s or merchant’s guild hires the adventurers
to figure out who or what is purchasing goods with very
old coins and jewelry. The culprits are a group of lizard folk
adventurers who discovered a cache of coins and jewelry from
a seemingly abandoned dragon turtle lair.
9 The last few groups of sewer cleaners have disappeared and
now sewage is starting to seep out into the street and is no
longer flowing out of the city as designed. Adventurers will be
hired to go into the sewers and figure out what happened.
10 A delegation of sea elves arrives to negotiate with a local
leader but they then disappear without a trace. Tensions are
already high between the surface and the sea elves so the
delegation must be found quickly.
CHAPTER 2 | Underwater CAMPAIGNS 21
Wilderness Underwater Encounters
Large bodies of water in the wilderness will tend to attract all Each of the following encounter examples is organized by
sorts of creatures and support larger natural and supernatural Challenge Rating and will list four encounters that you can
predators. Rivers and lakes deep within the wilderness are gain inspiration from, use as-is, or completely redesign
great locations for creature lairs, ruins, and ancient secret when you need a quick encounter underwater. Each example
places. The term wilderness can refer to any unexplored area assumes a party of four adventurers exploring an ocean
beyond the edge of the map, filled with strange reptiles, old environment, but some can easily be altered for use in
wastelands from ancient civilizations, strange geography, or rivers and lakes.
even a literal edge of the world depending on the campaign. CR 1 Underwater Encounters
Wilderness Underwater Adventure Hooks d4 Description
d10 Inspiration 1 Purple Nautiloid. The characters stumble across a large
(2d10) group of swimming nautiloids (ammonoids), and
1 Frontier settlements have begun reporting a strange orange one of them has a bright purple shiny metallic shell. The
foam floating down an uncharted river. The foam is toxic, characters can probably capture the purple ammonoid rather
and creatures are beginning to die off in record numbers. easily but if they kill it or otherwise harvest its shell, a sea elf
Adventurers are hired to travel up the river and investigate an finds out and tracks the party if possible. It will demand an
ancient underwater temple, dedicated to unknown gods, that is explanation or yell at their carelessness, but the sea elf will
assumed to be the source. not attack the characters. The purple ammonoid is rare and
worth 85 gp alive, or its shell is worth 8 gp.
2 A group of druids hires the adventurers to investigate why a
sacred mountain lake is losing water at an alarming pace. 2 Eight Tentacles, Zero Lockpicks. A giant octopus is
attempting to open a locked wooden chest at the bottom of
3 Royal scouts have tracked a dragon responsible for the the ocean. It is so preoccupied with its curiosity that it can be
destruction of farms and mining to an underwater lair in the easily surprised. The chest is a locked, air-tight, high-quality
remote wilderness. Every person sent to investigate further sea chest, and is currently filled with traveling clothes. If the
has failed to return. characters can secure the chest, the chest itself is worth
roughly 80 gp unless they or the octopus damage it. The
4 Fishermen have returned to port with a massive, never- chest has only been in the water for a few hours.
before-seen, corpse chained to their ship. It is displayed in
the harbor, and people from all around are traveling to look at 3 Blue Crabs. The characters find a crab that has been painted
it. A local religion believes it’s a sign of a coming apocalypse blue. The paint is slowly flaking off but something painted
and the adventurers are approached by multiple powers, this otherwise normal crab. If the characters can speak to
each hiring them to either prove or disprove that the strange the crab using any means, then it will tell them that it was
creature is just a creature or a religious sign or message. painted by a puny little dragon (kobold) and give directions to
a nearby beach. The kobold, if confronted, simply states that
5 A dark blob appears on the ocean’s horizon. It doesn’t get blue crabs taste better and that he was hoping to make more.
closer or bigger, but never leaves. Local adventurers are If threatened, he promises to stop and attempts to flee.
starting to make plans to explore it.
4 Curious Rays. The characters encounter 2d4 stingrays that are
6 A famous explorer is long past their expected return to more curious than normal, following the characters for 3d6
civilization. The adventurers are hired to retrace the explorer’s minutes before wandering off.
journey and return with news.
7 Recent frontier attacks were caused by goblinoids fleeing
some sort of catastrophe. The few that were captured and
interrogated report a two-week-long rain of green gelatin
after a mountain lake exploded. The adventurers are sent to
explore the area and figure out what happened.
8 A bright flash is seen over the horizon each night for the past
few weeks. It is in an uncharted area feared by most sailors.
The adventurers are paid to explore the area and figure out
what is causing the light flashes.
9 While exploring or traveling through the wilderness the
characters come across a large sinkhole, so deep that they
can’t see the bottom. But they can hear giggling children and
the sound of rushing water.
10 The characters are tracking the kidnapping of an important
humanoid. After a week of traveling the trail ends at a beach.
22 CHAPTER 2 | Underwater CAMPAIGNS
CR 2 Underwater Encounters CR 3 Underwater Encounters
d4 Description d4 Description
1 Pearl Bandits. Seven gnomes (thugs) are slowly exploring 1 Bronze Dancing Hell. The characters see a distant reddish
the bottom of the ocean using a box-like contraption that is pink glow below them. The glow is made up of roughly 50
generating a very painful squealing sound. If the characters slowly rising balls emitting every shade of red and pink light.
approach, they see the gnomes in brown leather armor, These balls are 3 hell sighs with roughly
clear glass helmets, and umbilicals attached to a weird 50 total decoys also floating and rising around them. The
vibrating box. An eighth gnome is floating dead in the water hell sighs will ignore the characters and slowly continue their
surrounded by blood, and another one is in the fetal position journey to the surface of the ocean. If the characters have not
clutching a bag with 10 pounds of irregular pearls. The other left the area after a few minutes, they will see a bronze dragon
six are attempting to defend themselves against three giant wyrmling swimming among them out of curiosity. So far, the
crown of thorns starfish. This battle should be difficult if hell sighs have ignored the wyrmling and the wyrmling has
the characters attack both sides at once. You can either not tried to eat one.
determine how the mechanism grants the gnomes water
breathing or have the machine conveniently explode when the 2 Beautiful Mine! The characters see a gleaming reflective
encounter is over. round shield that has no corrosion or barnacles near a large
coral reef. If the characters investigate, then the coral reef
2 Scent of Blood. One of the characters cuts themselves on is made up of a few sections of toxic (irritant) coral (as
something (a reef, a weapon, etc.) and within a minute 2d4 explained in Chapter 3) and five brain corals which will attack
reef sharks arrive and attack unless the characters find a the characters if they come within 5 feet of the shield. The
way to scare them off or otherwise direct their blood frenzy brain corals are fascinated with the shield and are trying to
elsewhere. determine what it is when the characters show up. The shield
is a shield of psychic damage resistance (magical shield that
3 Get ‘Em! 3d4 kuo-toa attack the characters. If any kuo-toa are gives whoever is wielding it resistance to psychic damage)
captured alive and interrogated, they claim that the characters that is also immune to corrosion. If the shield is exposed to
attacked them earlier and they just wanted revenge. This is air, then it will begin to disintegrate and will be destroyed
either a case of mistaken identity or an example of the general after just 1 minute if it is not completely re-submerged in
warped sense of reality associated with most kuo-toa. water.
4 Not Here For You. The characters encounter a motionless 3 Snakes! One of the characters stumbles into a rock or
slithering tracker that is not interested in them at all. It has disturbs debris where 1d4 swarms of poisonous snakes hide.
fed recently, so it will look like a blue-brown sphere of water The snakes will attack for two rounds and then flee if able.
floating nearby. This tracker’s particular madness means
that it only attacks merfolk and sea elves but will make an 4 Dolphin Bullies. 1d4 + 1 wavecutter dolphins notice
exception if the characters bother it. the characters and slowly approach them and begin a
conversation. After a few words, they quickly become
belligerent and insulting, demanding that the characters
“go back and burn in the sun.” The dolphins flee if the
characters resort to violence to get rid of them. If any of the
dolphins survive, they will tell anyone that listens about their
encounters with the “psychotic surfacers.”
CHAPTER 2 | Underwater CAMPAIGNS 23
CR 4 Underwater Encounters CR 5 Underwater Encounters
d4 Description d4 Description
1 Naked Pirate in Trouble. An escaped and naked slave (bandit 1 Hags in a Helmet. The characters find a gigantic rusty
captain) is trying to swim up and out of the ocean. They run bascinet helmet at the bottom of the ocean that is thirty feet
out of breath in one turn and will drown unless the characters in diameter with what looks to be bead curtains covering the
save them. If the slave survives, it will thank the characters and only entrance. Inside are three sea hags currently arguing
pretend to be a merchant captain captured by sahuagin. This over which taste better, sea elves or wood elves. If they notice
is partially true; the slave is a pirate but will only admit this if the characters they will ask for their opinion. This is a hag
the characters press for details. If pressed, the slave admits to coven in its lair. The characters can chat with the sea hags, or
having a cache of treasure that they can lead the characters to possibly trade with or attack them.
in exchange for their freedom. How the slave ended up in the If this coven is attacked, then one of the hags will break open
middle of the ocean is up to you, or the escaped slave may have a roughly polished purple globe which then emits a high-
no idea how they escaped or what held them. pitched shriek and a bright pink flash. If the characters are
still in the hag lair three turns later then they are attacked by
2 Fire Water. The characters notice that the water seems to a swarm of jellyfish on initiative 20. This swarm will attack
be getting warmer and one of them spots a huge column everything, including the hag coven. If the characters defeat
of billowing black soot bubbling through the water. A everything, then include another purple globe (that also
hydrothermal vent is the cause of the soot and if characters summons an uncontrollable swarm of jellyfish if broken)
approach, they will find 3 deep-water snails and very pale amongst whatever other treasure and oddities you want the
salamander-like fish (tiny fish) floating in and out of the soot characters to find.
column. The snails are likely to ignore the characters unless
attacked. Characters that insist on swimming directly in the 2 Sinking Ship. While near the surface, the characters see a ship
vent will take 3 fire damage per turn unless they are immune beginning to sink. Humanoids are attempting to jump or fall
to fire. This damage ignores fire resistance gained by being off the ship and at least 15 are currently swimming. A school
submerged. of 2d4 hunter sharks is nearby and circling the swimmers. The
ship will sink at a rate of 5 feet every turn and then at a rate
3 Thirteen Selkie. The characters come across a strange sight of 30 feet every turn after a minute. The ship can have trade
-- a group of 13 seals are swimming back and forth to the goods, treasure, or slaves that will drown if not rescued. This
surface carrying goods, equipment, and loot out of a recently encounter can be used to create a moral dilemma if the DM
sunk longship. The seals are selkie vikingr and they will ignore makes the characters choose between rescuing either slaves
the characters unless provoked or spoken with. Their ship or the humanoids, some of which might also be slaves or
was recently sunk, and they are just gathering everything they slavers themselves. There is no way to immediately tell.
can carry back to the surface. They all behave rather stoically
and are not overly concerned about their destroyed ship but 3 Terminal Grapple. Two young white dragons crash into the
are concerned with how they will get a new ship. ocean near the characters. Each is trailing blood, and they
seem to have fallen from the sky while trying to claw each
4 Where There Are Sharks. A wereshark sees and attacks the other to death. At the beginning of each of their turns, they
characters. Neither group is surprised and the wereshark will both sink 30 feet towards the bottom of the ocean and will
flee if it is reduced to less than half of its hit points. continue to grapple, bite, and claw each other until one of
them dies. The survivor will likely be very wounded and
immediately flee after killing its enemy for it won’t be in any
shape to then fight the characters. If the characters attack the
dragons before one of them wins, then they will immediately
attempt to slay the characters before continuing to murder
each other. They can each hold their breath for 18 minutes
and neither is worried about drowning before they kill the
other dragon.
4 Lager Elementals. The characters encounter two strange water
elementals guarding a long-dead (bleached) reef. These water
elementals are the color of pale beer for a reason you can
invent or leave as a mystery. They will attack anything that gets
within 15 feet of the dead coral reef.
24 CHAPTER 2 | Underwater CAMPAIGNS
CR 6 Underwater Encounters CR 7 Underwater Encounters
d4 Description d4 Description
1 Bubbling Door. The characters come across a natural shelf 1 Vacancy Lure. The characters see a flashing red light in
of rock with a thirty-foot gap beneath it. Something under the distance that flashes every 30 seconds. If the light is
the shelf is creating a constant stream of bubbles. The side approached, they soon realize that the light is coming from a
of the shelf that the characters can’t see is a portal to the magic sign that states in Common and Aquan, “Hero’s Rest:
Elemental Plane of Air. Two air elementals emerge and slowly Vacancy.” The sign also has an arrow pointing to a 20-foot
wander around poking and prodding at the environment with diameter air-filled glass dome with a very lavish restaurant
obvious curiosity. These elementals are not violent and will and bar. Inside the dome there appears to be two scantily
not prevent the characters from entering the portal if they so clad and bored elves. This is an illusion created by an eye
choose. This portal is two-way, and the characters can travel of the deep. If the characters do anything other than swim
back and forth, but the portal will close in 7 hours, only to past, then the eye will attempt to get beneath them and then
open again in a year. surprise them.
2 Pale Embrace. The characters see a pale blue flash in the 2 Aboleth Remnant. The characters encounter a bright ivory
distance and various sea creatures flee towards them. If the pyramid at the bottom of the ocean. It has no barnacles,
characters investigate, they see a drowned human woman plants, and no life seems to have taken hold closer than 100
dressed as a pirate embraced by a pale blue winged ghost of feet from each edge of the pyramid. A large 30-foot-wide
indeterminate gender that is either kissing her or giving her hole in one side looks like it was bashed in. This hole reveals
mouth to mouth. If the characters interfere then the pirate is how very thin the pyramid walls are: each no thicker than an
dead, and the ghost attacks them in a rage. In two rounds, eggshell. There is a faint purple glow coming from inside the
a second ghost rises from the dead pirate’s chest and also pyramid. If the characters enter the pyramid, they encounter
attacks the characters. 5 chuul guarding a large black rock roughly 10 feet wide.
If the characters do not interfere then both the ghost and the Under the rock, the chuul have been gathering treasure and
pirate fade from existence. The characters just witnessed the awaiting the return of the aboleth empire. This treasure can
Pale Lady, described in Appendix A, creating another Pale Lady be anything that you need it to be and should be easy to find.
warlock who will return to the Material Plane in five years.
3 Petrified Victim. Thirteen chwingas (described in Tomb of
3 Journey of Sojourner. The characters encounter the unique Annihilation) suddenly materialize around the characters and
golden-horned narwhal named Sojourner, fully described begin to pantomime and gesture towards a fourteenth one
in Chapter 8. She will be friendly and try to strike up a that has been turned to basalt (petrified condition). If the
conversation with them and is looking for a sahuagin that characters find a way to remove the petrification or otherwise
fled in the character’s general direction. She has a good seem to genuinely care about the fate of the chwinga, then
memory and will trade directions and stories. However, if she each character is granted a magical gift once. This gift is
is attacked, she will likely flee to gather information on the explained in the chwinga creature description.
characters so that she can decide if she needs to gather allies
to rid the ocean of them later or have something else do it. 4 Mermaid Bounty. A large group of eighteen merrows is angrily
searching a small kelp forest. Their prey escaped minutes
4 Sargasso Fish Hook. The characters find a fishing line with before and the merrows have failed to find her. The characters
a hook attached to it at a depth in the ocean that makes no can attack, avoid, or speak with the merrow, at which point
sense. If they follow the line, it leads all the way to the surface they will ask if they saw a mermaid with pink hair and evil
but a massive mat of woven plants is blocking most of the eyes. They will then offer a large bag of irregular pearls as a
sunlight (this is a sargassum collective) with an insane hermit reward if the characters can bring them her head as proof of
(bandit) attempting to fish off the side. The hermit is using her death. They refuse to explain what the mermaid did to
an overturned 15-foot boat as a house and he has no food anger them.
or water left. If the bandit is talked to, he will utter complete
nonsense but trade treasure for food and water. This treasure
can be whatever you want it to be. The sargassum will ignore
the characters unless they attack it.
CHAPTER 2 | Underwater CAMPAIGNS 25
CR 8 Underwater Encounters NWAWnoaardtteaearrn,l,lywwtdhaarettoeepbrr,o,taeeovrvedderrrsyiyndwwkid.hhseerhreer,i,nk;
The very deep did rot...
d4 Description UYthpeaaon,tsetlvihmeerysttlhihmiinsygsssheadou.idldcbrae!wl with legs
1 Champagne Clouds. The characters encounter 3d4 lion’s – The Rime of the Ancient Mariner,
mane jellyfish that are floating on the surface. They are so Samuel Taylor Coleridge
massive that they make the water under them darker. These
creatures will likely ignore the characters unless attacked.
2 It Was This Big. Three enormous bluefin tuna (gargantuan
fish), each 40 feet long, decide that the characters look tasty
and begin to approach them. The fish can be easily scared
off if the characters use bright light or manage to cause them
serious damage. Otherwise the fish attempt to swallow one
character each and then swim off in separate directions.
3 Tentacles for Dinner. The characters encounter a giant squid
and two killer whales locked in battle. If the characters do
nothing, the whales will eventually kill the squid and swim
away with their meal. If the characters attack then the animals
are likely to attack anything that gets near them in the chaotic
underwater melee.
4 Dead Meat. Three great dungeon crabs are slowly tearing
apart the corpse of a blue whale. They fiercely attack anything
else that comes near, and sometimes each other. The
characters also see a wounded sahuagin attempting to hide
in what is left of the whale’s stomach, but it won’t be able
to hide from the crabs for much longer. If the sahuagin is
rescued it will grant one of the characters a death debt and
offer a life of service. This can be either amusing or very
annoying depending on how you want to handle this possible
character minion.
26 CHAPTER 2 | Underwater CAMPAIGNS
CR 9 Underwater Encounters CR 10 Underwater Encounters
d4 Description d4 Description
1 Misplaced Illusion. This encounter involves the spell, 1 Kelp Ambush. The characters are swimming near or through a
programmed illusion. The spell was cast near a wild magic massive kelp forest filled with a wide variety of sea life swirling
zone and forced to the bottom of the ocean. This spell is around a bright yellow light when they are attacked by 2d6
permanent until dispelled and recycles every 10 minutes as shambling mounds. These creatures will not pursue characters
long as a humanoid is within 120 feet of it. You can make this that flee but there is visible treasure from past victims near
a living spell if you have access to Icewind Dale: Rime of the the blindingly bright yellow light. The light is being emitted by
Frostmaiden, but it is not necessary for this encounter. an ancient gold coin that glows as bright as the sun (creatures
The characters get within 120 feet of the programmed illusion within 15 feet of it must make a DC 10 Wisdom saving throw
and it activates, playing out the following scene. or be blinded permanently). This coin’s light counts as magical
“An old dwarf is trying to get a strange iron wagon out of the sunlight and it cannot be dispelled but the coin can be painted
mud using a team of mules. He gets angrier and angrier and over, buried, or otherwise “shuttered.”
uses all manner of curses on the mule team. As he frantically
works to get the mules to help free the wagon, you see the iron 2 Signpost. The characters find a floating wooden signpost with
walls of the wagon slowly distend as if something trapped within haphazardly cut and poorly painted signs pointing in almost
it was pushing a claw against cloth and not iron.” every direction and all labeled, “SHOP.” The wood is dry,
If the characters watch for more than a turn then the scene obviously enchanted, and a little brass bell hangs from a nail
takes a terrible turn as all manner of wraiths and nightmares in the main wood post. If the characters ring the bell, then
escape the iron wagon and lay bloody waste to dwarf and an incredibly happy voice emits from the bell and tells the
mule alike. This illusion is incredibly detailed and graphic. characters where the closest shop is (this can be on the surface,
All creatures with an Intelligence higher than 5 must make in an aquatic humanoid civilization, cave, etc.). The shop exists
a DC 17 Wisdom saving throw or refuse to watch the rest of and is owned by the unique marid, Bib Bum Bip, described in
the illusion and be compelled. Compelled creatures can only Chapter 8. The shop is run by a variety of humanoids who sell
use their actions to move far enough away from the illusion all manner of unenchanted items. If the characters mention
so that it cannot be triggered, at which point the compulsion wanting to buy or sell magical items, then they will be told to
ends. Characters have defeated this encounter if they find a wait a few days for Bib Bum Bip to return from a business trip.
way to dispel the 6th-level spell or otherwise make it so that it
can never trigger again. 3 Aquatic Standoff. The characters hear a conch horn in the
This encounter was inspired by Underfoot. distance; then they hear a loud boom quickly answer it. These
sounds seem to spar with each other for a few minutes if the
2 Poor Judgment. The characters encounter 1d4 sperm whales characters do nothing. If the characters investigate, they come
that will ignore the characters unless the characters get within across a group of sahuagin and merfolk in battle formations
60 feet, at which point the whales will attack the characters. staring at each other. Each group has roughly thirty to forty
The whales then flee after two rounds, having misjudged how members and they are about 200 feet away from each other.
edible the characters are. If the characters back one side, then this encounter is easy, as
the opposing side will lose. If for some odd reason they attack
3 Whaling Survivor. The characters encounter a wounded (270 everyone, then this encounter will be very difficult, as both forces
hit points remaining) blue whale with three large harpoons decide the characters are much more of a threat than each other.
stuck in its side and back. The wounds are beginning to fester The characters can also just ignore the stare down and leave.
but removing the harpoons is enough to save the whale from
a slow and inevitably fatal blood infection. Depending on The sahuagin force: 25 sahuagin, 3 sahuagin priestesses, 1
the characters’ actions, they can either befriend the massive sahuagin baron, and 1 giant shark.
mammal, ignore it, or possibly fight it. The blue whale is
particularly annoyed with humans at the moment and will The merfolk force: 30 merfolk, 3 merfolk raykeepers each on a
focus most of its attention on killing humans until it gets below giant stingray, 5 merfolk historians, and 1 merfolk princess.
80 hit points, at which point it will attempt to flee.
4 Predator Playtime. The characters encounter 2d3 ichthyosaurs
4 Bucket List. The characters see a large 60-foot-radius sphere of lazily swimming and bumping into each other playfully while
white frothy water slowly descending through the ocean. They tossing a shark’s head back and forth. The characters can
also hear dry coughing, giggling, and laughter coming from it. easily avoid this encounter, but if they linger the ancient
The sphere is the area of effect of an airy water spell (this spell marine reptiles will attack.
is explained in Chapter 6) cast by a semi-retired adventurer
on their ailing grandmother and her three friends (all are Content Warning
commoners). The grandmother is deathly ill and is dying of old Bucket List and “Right to Die.”
age. Her three elderly friends realized that they do not have
much longer to live and want to join their friend. They have all If you and your players can handle suicide specifically the
decided to see the bottom of the ocean before the spell ends, elderly and terminally ill choosing when and how to die then
knowing full well they will not survive after that. the commoners in this encounter are in the ocean on purpose.
They are all happy to spend their last few hours at the bottom
of the ocean and will explain this to the characters. They have
made their minds up and ask that their decision is respected.
They will gladly talk with pleasant characters but none of the
commoners have second thoughts or want to be rescued from
their inevitable fate at the bottom of the ocean.
Or, if you want, you can make this a cruel joke cast by an evil
wizard, at which point the commoners want to be rescued. It is
your campaign and only you know what your players’ needs are.
CHAPTER 2 | Underwater CAMPAIGNS 27
CR 11 Underwater Encounters CR 12 Underwater Encounters
d4 Description d4 Description
1 Wonderfall. This encounter describes the wonders of a fantasy 1 Observers. An archdruid (Volo’s Guide to Monsters),
ocean and is an example of an encounter without enemies to transformed using its wild shape ability into a giant shark,
defeat or problems that must be solved. The characters hear a and 2 other giant sharks, begin following the characters.
distant orchestral sound coming from inside a large 80-foot- They follow from a good distance and observe the characters
diameter dome of loosely connected living coral. Each entrance for three days. If the characters don’t do anything to harm
can easily accommodate a Large creature and the dome the ocean and otherwise behave themselves, then they will
radiates a deep sense of peace. If the characters investigate, eventually leave.
they will see all manner of creatures, prey and predator alike,
are slowly swimming along the inside edge of the dome. 2 The Mercenary. An ancient wereshark named Black Tooth
At the center of the dome’s ceiling is a silvery portal with large approaches the characters while in her hybrid form but
boulders falling out of it. The boulders fall slowly to the bottom immediately claims to only want to talk. She explains that she
of the ocean and then slip into another silvery portal. As the has heard of their exploits and is looking for some exquisite
boulders fall each emits an instrumental sound that travels violence. She offers to join them for one week, free of charge,
hundreds of feet through the water. The sounds are always to show what she can do: “we can negotiate a price later.”
concordant, but the orchestral music slowly changes and shifts Black Tooth has not decided if she will kill the characters or
as the boulders change. Each portal will not function for living not and will watch them over the next week. If they are strong,
creatures and any attempt to breach or dispel them will destroy she will join them; if they show weakness, she will attempt to
both portals. This dome is filled with so many creatures that if kill them when they are injured. If the characters refuse her
the characters decide to fight, they should be in mortal danger. offer, then she shrugs and leaves.
Any creature that destroys the music will enrage everything.
Each creature will attack whoever “killed the music” and be 3 Adventurers. The characters stumble across a group of
immune to any spells or effects that target their minds or adventurers from the surface, each of them magically breathing
emotions for three turns. If the characters are respectful, they water. You can either make the group from scratch or use the
can stay here for as long as they like and even rest (assuming following: Appomattox (mage), Rollo (gladiator), Pixtastic
they can breathe) without worry. (warlock of the Great Old One, see Volo’s Guide to Monsters),
Vermina (war priest, see Volo’s Guide to Monsters), Yolanda
2 Beautiful Nautiloids. The characters encounter a large group of (assassin), and add a few knights as nameless hirelings. The
2d10 + 20 giant ammonoids, slowly swimming towards them. adventurers will be wary of the characters and likely just wave
Each ammonoid has a slightly different shell pattern of red and and slowly swim past them and stare. Assuming this encounter
green swirls. These creatures can be ignored easily and will not doesn’t immediately devolve into violence, Vermina will hail the
attack unless provoked. characters right before they leave and ask if they have seen a
gigantic golden carp anywhere nearby. She claims that it is 80
3 Exit Door. The characters see a purple painted wooden door feet long. She is clearly highly intoxicated and the carp may or
(sized for a Medium creature), floating in the water. The door may not exist, depending on the needs of your campaign.
is magical and glows with bright white light. The characters
also hear the sound of wind chimes coming from it. Above 4 Ready, Set, Race. Five merfolk princes and princesses are each
the door is a stone bas relief of a hydra. If opened from this racing around some dangerous coral (roughly 4000 square feet
side, the door does nothing and the portal does not open. of pearl’s revenge coral, described in Chapter 3). Seven giant
This door is a portal to a dangerous swamp somewhere in the stingrays are also floating around and otherwise behaving just
world above, but the magical portal will only transport creatures like well-trained domesticated horses. The merfolk notice the
back and forth if a hydra is within 20 feet of either door. If the characters and motion them to join the merfolk. The merfolk
characters wait around, then three hydras wander near the will let one of the characters ride a giant stingray if they are being
door (on the surface side far away) and the portal opens. The respectful and the merfolk would like to make friendly bets on
characters can escape to the swamp and fight the hydras or the races. The merfolk have irregular pearls, gem-quality pearls,
ignore it altogether, but the hydras will sometimes stick a head and very expensive-looking live abalone mollusks to bet with.
through this door, look around curiously, and then wander off.
Underwater Druids
4 My Order Is Late! One of the characters gets a telepathic
thought in their head that goes something like, “took you long Of the character classes found in the Player’s Handbook, druids are
enough Bobert. I assume those are the slaves I ordered? Well, the easiest class to use in an underwater setting, for starting at 4th
bring them closer and we’ll see what you want for trade.” The level they can use wild shape to assume a shape that breathes water
character knows in what general direction the thought is coming and has a swimming speed. This is also true of most NPCs with
from. If the characters immediately flee, then a morkoth (Volo’s access to a feature like wild shape.
Guide to Monsters) will only pursue them for a round or two
before getting bored and wandering off. The characters can also
attack or strike up a conversation with it. Clever characters can
also talk their way out of this encounter if they are respectful
since the morkoth is only interested in acquiring slaves.
28 CHAPTER 2 | Underwater CAMPAIGNS
CR 13 Underwater Encounters d4 Description
d4 Description 4 Prison Break. An adult gold dragon is swimming as hard as it
can for the surface. It is covered in green glowing wispy chains
1 Mission Complete. The characters see a large group of sixty held by five strange fiends (farastus). Carceri and the gehreleths
warriors, all from various aquatic races, slowly swimming past are briefly described in Chapter 7. Each farastu is attached to the
at a distance. Leading them is a naked old human (archmage) dragon by 200-foot-long unbreakable magical chains created
leading a barbed devil on some sort of green metal chain. by a portal trap that triggered as the dragon fled Carceri. The
This force is returning to Isabella (Empress of the Sea), who farastu are doing their best, and failing, at pulling the dragon
is described in Chapter 8. The warriors are merfolk (guard), back to Carceri. But their efforts do reduce the gold dragon’s
locathah (see Ghosts of Saltmarsh), sea elf scouts, and a few swim speed to 10 feet. The farastus are immune to any damage
sahuagin. Each of the warriors serves Isabella out of fear, but caused by the dragon so long as it is chained to them.
the naked archmage and his odd pet devil have had their will If the dragon reaches the surface and the chains are exposed
completely dominated and serve her with absolute loyalty. The to natural sunlight, then the chains will evaporate. The farastus
characters can avoid this encounter, trail them from a distance, know this and will attempt to kill the dragon if it keeps trying to
attack, or strike up a conversation. If the characters strike up a flee to the surface, but they fear what will happen if they return
conversation then the naked human tells them to follow, “and without their prisoner. The dragon will ignore all attacks if it
meet Glory!” He will then start to giggle and say nothing more. can reasonably reach the surface and if the sun is shining. If the
characters attempt to rescue the dragon, then the dragon will
2 Gathering Components. An elf archmage with three potions of do what it can to aid the characters in their fight.
water breathing attempts to greet the characters and offer them
400 gp per narwhal horn they collect. He claims that hunting Portal Traps
them down has been “incredibly tedious” and is now prepared
to just pay for the horns, for he “just can’t stand getting sopping Most of the portals leading out of Carceri lead to the abyssal or
wet!” If the characters agree, then the archmage tells them hadal zones of the oceans, and those easiest to get to or use all
where they can meet in two weeks. The archmage may be have convoluted magical traps or surprises for anything that uses
convinced to give away his remaining potions if the characters a portal without permission. The portal used in this encounter is
are persuasive or well-behaved. always open, but any creature that passes through it is attached
to a few farastus. Other trapped exit portals only allow the body
3 Forgotten Guard. An aboleth watcher is guarding a large to leave, and the mind stays behind, stored in a nearby object
cave entrance as the characters swim past it. The creature until the body returns. Another casts a geas that forces the victim
will not stop the character or otherwise bother them but will to push twenty poor souls back into the portal in the next year
warn them once to not enter the cave if they approach. If the or die. There are also more conventional traps like feeblemind,
characters attack and defeat the aboleth, then place whatever finger of death, flesh to stone, etc. The main idea is that a creature
treasure or terrible surprise you want in the cave. may be able to escape Carceri, but it will pay a terrible price or be
drawn or coerced to return.
CHAPTER 2 | Underwater CAMPAIGNS 29
CR 14 Underwater Encounters CR 15 Underwater Encounters
d4 Description d4 Description
1 Where Fools Dare to Swim. The characters encounter a 1 Date Night. A married pair of storm giants are enjoying a
strange area while traveling underwater. A massive volume deep swim and mostly goofing off while pretending to look
(roughly 5 cubic miles) of ocean has been marked by orange for pearls. Although they are not wearing armor, they have
immobile pulsing globes of light. Each globe is roughly 50 seen the characters. One of them waves to the characters
feet distant from each other and they collectively mark a and smiles. This couple is very friendly, and they have a love
massive three-dimensional net of pulsing globes. 10 feet for pearls and giant clams. They are a wealth of information
past each globe is an area of dead magic. See antimagic on the local water and nearby aquatic civilizations if the
field in the Player’s Handbook for a description of a dead characters behave themselves. They can also trade with the
magic area. This area is enormous and was marked off by an characters and have a large collection of irregular pearls.
ancient civilization that no one remembers. Each globe can They have three grown children (storm giants) that will arrive
be temporarily destroyed or dispelled easily, but they always within 5 turns if the couple calls for help.
return three hours later. The giants live in the ruins of an ancient civilization that
is roughly 400 feet away. They have rearranged the marble
2 Filthy Demon. The characters see something (a wastrilith from bricks and other usable building bits into a longhouse of sorts
Mordenkainen’s Tome of Foes) moving very quickly through the and enchanted it to be filled with air. They use a command
water, trailing a brown film. It catches up to a massive shark word that allows them to enter through the main door
and tears it to pieces. It then spends a few moments frantically without letting the water flow into their repurposed building.
tearing through the shark’s stomach looking for something. If
the characters approach or attack, then the demon will fight 2 Bubble Trap. The characters come across an air-filled blue
until it gets to half of its hit points and then attempts to flee. If sphere, 15 feet in diameter. Inside the sphere are a few
the characters do nothing, then the wastrilith quickly swims off mummified corpses and a collection of various items and
in a different direction. treasure, including an opened treasure chest. The inside of
the sphere is covered in thin flaky brown smears. A granite
3 Never Quenched. The characters start to feel a slight menhir has been erected near it, with words carved into it.
current that is pulling them towards the ocean floor. At this
distance, the characters can easily avoid the cause and if they The writing is in the Common and Gnomish language.
are observant, they will see small creatures and silt slowly “Here lies Glimbly ‘No Trap Can Hold Me’ Meezey. He couldn’t
drifting down. If they investigate further, they will realize that keep his hands out of my pockets. Even dying of starvation, this
something at the bottom of the ocean is pulling water into proud idiot refused to apologize.”
itself like a three-dimensional drain. The currents will get
steadily stronger and more dangerous if the characters keep This blue sphere is a magical trap that allows creatures and
approaching. The culprit of the strange drain is a temporary their equipment to pass into it but anything attempting to
portal roughly three feet wide that leads to the Elemental leave finds that they are in a permanent spherical wall of
Plane of Fire. The portal will close in 2d3 hours and not force. If a creature cannot destroy or dispel this sphere, then
reopen. they are trapped until they starve to death. Remember that
this spell effect penetrates the Ethereal Plane and most
4 Greed is Painful. The characters discover a 300-foot-long movement spells (dimension door, etherealness, misty step,
ivory tusk laying at the bottom of the ocean. The tusk is etc.) will not allow a creature to escape, but teleport or plane
not magical, weighs roughly 8,000 pounds, and is worth shift spells will. Place whatever treasure you want within the
considerably more (1,500,000 gp) if it can be moved as one sphere, but the oldest corpse should be a gnome rogue. If
piece. If cut into manageable sections, then the ivory is worth you want this trap to be even nastier, fill it with a few ghosts
12 gp per pound. The characters will have issues looting the who are also trapped in the sphere.
tusk because there are currently two very large undead hordes
slowly wandering around and over it. 3 Ancient Command. The characters see a massive crater
If the characters do not come up with a clever plan, then surrounded by debris. At the center is an iron golem solemnly
chances are high that the tusk is damaged or that unwanted working to make the crater deeper. How long it has been here
attention arrives to investigate the noise the characters slowly trying to “find the center of the world,” is up to you,
cause trying to fight the undead hordes. This encounter can but its creator died before it could reword the command.
quickly get bogged down if the characters want to just wade
into the undead mass. If that happens, you may need to 4 Personal Space. A marid approaches the characters and asks
run the higher CR undead as normal and then just assign a if it can inspect them. It is looking for a fugitive. It refuses
small amount of damage per round for those surrounded by to explain who the fugitive is but would like a look at the
the undead horde. This encounter is designed to make the characters. Its demands will get more and more outrageous
characters think their way past the undead and then think of and invasive until the characters threaten it with violence. It
a way to quickly grab this very heavy and large treasure -- or it will then complain loudly about useless creatures as it flees.
can also slay the foolish.
Undead Horde 1: 82 skeletons, 32 zombies, 18 ghouls, 8
ghasts, 8 wights, 5 vampire spawn.
Undead Horde 2: 132 skeletons, 3 bodaks (see Volo’s Guide to
Monsters).
30 CHAPTER 2 | Underwater CAMPAIGNS
CR 16 Underwater Encounters CR 17 Underwater Encounters
d4 Description d4 Description
1 Madness Beckons. While traveling through the ocean, 1 Journey of the Demodand. Demodands, gehreleths, and
the characters see a very bright green flash below their Carceri are briefly explained in Chapter 7). A shator is
location. After a few seconds they hear a massive boom. exploring the ocean to find a one-way portal to Carceri that
The characters can ignore this, or they can investigate. Two none of the gehreleths were aware of. The demodands
thousand feet below them is an aboleth, a shaboath golem, recently had adventurers sneak into Carceri and they want
and five skum attempting (and failing) to blast open a the portal found and guarded. The shator will attempt
gargantuan oyster easily 400 feet wide. The aboleth and its to greet the characters warmly and ask them if they have
minions will immediately attack if the characters are spotted. found any large iron circles in the ocean, exactly 33 feet in
Inside the oyster, which opens easily if no aberrations are diameter. The shator will not explain what it is or how to turn
within 300 feet of it, is a stable one-way portal to the Far the portal on but will be willing to purchase the information
Realm. Once opened, the oyster remains open and will not or trade a magic item if the characters can find it, for the
close unless an aberration approaches. shator has been searching for a while and is beginning to
lose touch with Apomps and wants to return. It will agree to
2 Wait! Let’s Work Together. A juvenile kraken (see Ghosts of meet the characters anywhere of their choosing in a month
Saltmarsh) attacks the characters but quickly attempts to and can promise up to a rare magic item in exchange for the
parley when it realizes how powerful they are, offering to give information. If the characters attack, then the shator will use
the characters all the loot if they help it clear out a giant lair its scroll of etherealness to flee, watch, and possibly attack the
that it wants to move into. The characters can agree, refuse and characters later with gehreleth reinforcements.
leave, or attempt to kill the kraken. The juvenile will likely flee,
having no desire to slug it out with creatures of such power. 2 Death Eater. The characters encounter a glowing whale
If the characters agree to help the kraken, then it wants help skeleton (Yesteryear is explained in Chapter 8) that is fighting
killing the giants from “Date Night” in the previous encounter twenty-three wraiths. Before the characters decide what to
list. The kraken will likely claim there are only two giants that do, Yesteryear annihilates one of the wraiths with a bright
need to be slain unless pressed for details, in which case it will ray of energy. If the characters do nothing, then Yesteryear
admit that there are five of them in total. will quickly annihilate a few wraiths and the others will flee.
If the characters attack Yesteryear, it will ignore them unless
3 Swallowed Treasure. A dragon turtle is tearing up the bottom one of them is undead. If they manage to cause more than 50
of the ocean in search of something. This encounter happens points of damage against it, it enters the Border Ethereal and
at a distance that allows the character to easily avoid the wanders to another ocean in another Material Plane. If the
creature if they wish. Observant characters may note light characters help Yesteryear, then it will chat with them for a
ship wreckage slowly drifting down from above. The dragon few minutes before excusing itself to feed elsewhere.
turtle will quickly find an iron chest, swallow it, then wander
off to its lair. The turtle will travel for over two days to reach 3 Four Quarters Key. A glowing silver coffer giving off bright
its lair and it will likely notice the characters following it red light out to 20 feet is sinking through the ocean near
after a while, in which case it will turn and attack them. The the characters. The characters can ignore it, follow it to the
chest is enchanted and heavily trapped -- filled with whatever bottom of the ocean, or intercept it easily. The coffer is not
treasure you want to place in it. magical or locked, weighs roughly 20 pounds, and is worth
80 gp. If opened, the inside contains a wooden void that used
4 Undying Indigestion. An old and horribly scarred jaw worm to hold an oversized key, but only a quarter of the key is in
is making its way to the surface from the abyssal zone the coffer. The key is magical and will mend itself if brought
because it has a terrible stomachache and has been driven within 10 feet of any other of its fragments. The location of
mad with pain. The jaw worm only has half of its hit points the three other fragments and what the assembled key does
and will completely ignore the characters as it attempts to or doesn’t do is up to you. As an example, it could unlock a
move to the coast. If the characters kill the jaw worm, then prison door in Carceri and free an insane and volatile (chaotic
its stomach bursts and three irritated vampires try to flee evil) empyrean.
because the running water prevents some of their powers
from working. They will go out of their way to avoid combat 4 Riddles and Whalers. An enigmatic serpent suddenly appears
but if cornered will fight to the death. The vampires fully and asks one of the characters if it is (insert the character’s
understand the danger they are in while in the ocean. name) from (insert where the character is from). It will
ignore the other characters unless they become violent. If the
Oceans and Vampires character speaks the truth, then the enigmatic serpent will
offer to trade them a riddle. This serpent has it in its head
Vampires in the Monster Manual have a variety of weaknesses and that it will ask the next three whaling ships the character’s
vulnerabilities inflicted upon them if they are in running water. riddle. If the whalers get the riddle correct, then it will allow
In my campaigns they all apply in the ocean, except for acid them to return to port with whale corpses. This will all be
damage. I want the oceans to weaken my vampires, not boil them explained to the character. If the character lies about who they
in acid. Feel free to change any of this as you see fit. are then the serpent will say, “well then, you are completely
useless, aren’t you” and wander off.
CHAPTER 2 | Underwater CAMPAIGNS 31
Marble Path Day 13-21. The king and his retinue camp near the end of
to Immortality the path and await the serpent’s arrival so that it can distract
the kraken. During this time, the king decides that he would
Marble Path to Immortality is an idea seed that you can rather just pass away -- creating a sudden problem. Who will
build a more detailed or complicated adventure around that take the third spot and become immortal with his daughters?
can challenge characters of any level. If your characters are Will it be one of his daughter’s lovers, the archmage, the
prone to seeking violent solutions, then they should be level spymaster, one of the players’ characters? This is when things
17 or higher. In this section, you will see a timeline, a brief can truly get violent.
on the creatures and NPCs involved, and some suggestions
for adventure twists and possible activities based on your Day 21. Whatever remains enters the immortality dome and 3
character party’s general alignment and behavior. maruts (see Mordenkainen’s Tome of Foes) explain that three
will become immortal after a year of service. They will explain
Your campaign likely has no area with a large empire and an nothing more but will point at three triangular platforms.
old king that you can kill off to support this adventure. If this What service the maruts require is up to you.
is the case, then one of the king’s first stops with his entourage
needs to be a portal from his Material Plane to the Material Suggested NPCs
Plane your campaign is in. The NPCs in this adventure are
camping under the ocean using the spell, utility, described The king is an adventurer-turned-emperor named Musa Keita
in Chapter 6. the First (his statistics are located in Chapter 8). Both of his
daughters are mages. The royal retinue also includes an old
Brief wizard (archmage) and a spymaster (assassin) and at least
20 other NPCs (commoners, thugs, knights, etc.). The king
A king (Musa Keita the First) is dying of a wasting disease will also command the absolute loyalty of a dao genie until day
(cancer). This wasting disease will always come back to ravage 12. If you want to further complicate the possible violence that
Musa’s body after being magically cured or removed. The royal this adventure can generate, have only one of the NPCs (other
court has been draining the coffers to keep him alive with than the king) able to cast or use a device that makes use of
various spells and potions, but he won’t stand for it anymore. the spell utility, as described in Chapter 6. The royal retinue
As a retired adventurer, he takes his two surviving daughters has been using this spell to rest and camp under the water.
with him into the deep waters to hunt out an ancient myth
about the Marble Path, described in tales as a harrowing path Party Actions
to find immortality. All that he knows, in the beginning, is that
the path starts underwater, a strange and aloof creature knows Good Party. A good party can help mediate or calm down
how to start the path in exchange for a treaty, and three people potential violence during Days 13-21. The king refuses any
must become immortal at the same time or none of them can. magical aid to prevent him from dying, and this trip has helped
Musa Keita the First is further explained in Chapter 8. him come to terms with his life and death. A good character
may even be talked into marrying a daughter in exchange
Timeline for immortality. If your campaign needs one of the king’s
offspring to be a son (or genderless, gender-fluid, etc.), then
Day 0-3. The king travels to an enigmatic serpent’s feel free to change the gender.
underwater lair and signs a treaty allowing it to inspect 1
out of every 10 ships leaving his empire’s main port city for Neutral Party. A neutral party will likely decide to back
anything looted from the sea. If anything is found, the serpent is whoever they want to become the third immortal now that the
encouraged to make a violent example of the ship. In exchange, king accepts his mortality. This can end in violence or some
the serpent tells the king where the Marble Path starts and very crafty roleplaying. A neutral party might still argue and
what he needs to bring with him to be successful. The serpent fight amongst themselves if one of them wants to take the
also promises to meet the king at the “immortality dome,” and third immortal spot.
distract a kraken long enough that the king and his retinue can
safely enter the dome and negotiate with its keepers. The royal Evil Party. An evil party might go as far as to sow discord
retinue may or may not use a magical portal to move to a more and wait for the different factions to kill each other before
convenient Material Plane that will not drastically change the sweeping the field and taking all three immortality positions
power structure of your campaign’s surface world. for themselves. If there are more than three characters in
the party, then you should expect further bloodshed as the
Day 4-12. The king travels along the Marble Path at the party fights amongst themselves for the three immortal
bottom of the ocean with his retinue. They make at least three positions. As a further complication, if the evil party gets
stops, one to deposit 1000 iron coins, one to deposit 1000 overly murderous and only one or two remain, then neither
platinum coins, and one to free a slave or servant from service will become immortal, for the maruts are creatures of
(the king releases a dao genie that has been in his family’s pure law and there is no negotiating with them. There
service for four generations). Each location can be the ruins must be three immortals created at once. If the maruts are
of an old civilization, an unassuming hole, or an enchanted destroyed, then the immortality dome collapses and no one
marble pedestal. becomes immortal.
32 CHAPTER 2 | Underwater CAMPAIGNS
CHAPTER 2 | Underwater CAMPAIGNS 33
CHAPTER 3:
DIFFICULTIES AND ODDITIES
34 CHAPTER 3 | Difficulties and Oddities
Water Hazards - Natural Rainbow Slick. This supernatural bloom is usually a bane
to large cities or areas contaminated after heavy magical
All water is hazardous to creatures that can drown in it. Most experimentation. This bloom creates a very slick surface that
of the following additional hazards assume the characters floats on the water and coats anything unfortunate enough
are adventuring in the oceans, but swamps, flooded to get caught in it. Tiny or smaller creatures will begin to
dungeons, rivers, and lakes will have most of the following suffocate if they cannot find a fresh water source. If the slick
hazards as well. is ignited, then the entire slick will burst into flames, causing
4d6 fire damage to everything within 5 feet of the water
Algae, Seaweed, surface. Creatures not in the water and not covered in the slick
and Seagrass Meadows can make a DC 12 Dexterity saving throw and only suffer half
as much with a successful save. The rainbow slick will then
Algae and seagrass can form massive underwater meadows in continue to burn for 2d12 hours as it is slowly consumed; the
shallow (not normally deeper than 100 feet) water with some surface of the water is literally on fire. Strangely enough, these
of the blades of “grass” extending beyond ten feet in length. flames produce no smoke at all, and humanoids witnessing it
Moving through these meadows is not difficult but anything for the first time may stare in wonder or flee in terror.
inside the meadow will be heavily obscured. These are great
places to hide, as well as be ambushed suddenly. Seagrass Meadows and Forests. These plant masses can
be deceptively difficult to travel through as the vines and
Algal Blooms. Most natural free-floating algae are harmless stalks get tangled together. These areas are difficult terrain to
or in such low concentrations that they are harmless. Blooms anything not Tiny, Gargantuan, or Colossal in size. The new
occur when the conditions allow for massive concentrations Colossal creature size is explained in Chapter 7. Creatures
of algae in one place and can come in a variety of colors more than 10 feet apart have half cover to each other, and
from mustard yellow, blood red, emerald greens, and even visibility usually does not exceed 20 feet. These areas can be
bioluminescent blue that glows at night. These blooms create exceptionally dangerous places where creatures can attack
heavy obscuration, but some are also harmful. A rare and with little to no notice. Any attempt to determine direction is
supernatural algal bloom has been documented that creates a attempted at disadvantage while inside a seagrass meadow or
rainbow-like slick surface on still ocean water. forest. On the other hand, food is plentiful in these areas, and
Wisdom (Survival) checks should automatically succeed. Five-
Dark Dreams. This supernatural bloom only occurs rarely foot-cube sections of meadows and forests can be destroyed,
and on cold nights with no moonlight. This invisible algal and have an AC of 10, 15 hit points, and are resistant to
bloom has no smell but living creatures within a few dozen bludgeoning, piercing, and slashing damage.
feet of the water’s edge will start to be covered in a fine brown
dust that resembles pollen. Creatures with an Intelligence Bluescale Whips. This supernatural seagrass is incredibly
higher than 3 will have trouble determining friend from foe irritating to any creature that touches it. It can be identified
and otherwise behave in a confused and belligerent manner by a DC 10 Intelligence (Nature) check, but it is easy to
unless they make a DC 11 Charisma saving throw. Fey accidentally stumble into this irritant if a creature is moving
creatures are immune to this bloom. quickly or not paying attention. A creature that passes
through a five-foot section of bluescale whips must make a
Hypoxic Bloom. Some blooms simply reduce the usable DC 5 Constitution saving throw or suffer disadvantage on all
oxygen in the surrounding water so suddenly that even mobile Dexterity saving throws and ability checks for an hour. This
sea creatures die before being able to escape the dead zone effect is considered a poison. The DC increases by 1 for each
created by this bloom. Dead Zones are explained later in five-foot section of bluescale moved through, to a maximum
this chapter. DC of 15. A creature makes one saving throw at the end of
their turn, once per turn.
Poisonous Water. Some blooms turn the surrounding water
poisonous (usually cyanide) to those that drink or breathe it. Grey Marley. This supernatural seagrass is hard to find
Those that drink this water must make a DC 10 Constitution because most aquatic humanoids pick and harvest this
saving throw or gain the poisoned condition and take 1d6 rare seagrass when it is found. Grey marley is usually
poison damage. Those that breathe this poisonous water hidden deep within a kelp or seagrass forest. Grey marley
gain the poisoned condition and then must make a DC 10 is covered in small onion-shaped gray nodules that, when
Constitution saving throw at the beginning of each of their eaten, have the same effect on a creature as if they had drunk
turns. They take 2d6 poison damage on a failed save, or half two alcoholic beers. Some of the grey marley nodules are
as much on a success. poisonous but difficult to differentiate, so those who fail a DC
15 Intelligence (Nature) check will not be able to tell them
Poisonous Gas. Very rarely, a bloom will create poison gas apart. Poisonous grey marley is intoxicating but it also forces
(hydrogen sulfide) that will threaten air-breathing creatures a DC 12 Constitution saving throw or the eater gains the
near the water. This gas comes with a terrible stench and all poisoned condition.
natural creatures will flee from it. Those that can’t escape are
affected as if they are in the area of effect of a cloudkill spell.
CHAPTER 3 | Difficulties and Oddities 35
Buoyancy Frigid Water. A creature can be immersed in frigid water for
a number of minutes equal to its Constitution score before
Buoyancy is usually ignored in fantasy games because of how suffering any ill effects. Each additional minute spent in
crunchy (density of the object, water density, neutral buoyancy, frigid water requires the creature to succeed on a DC 10
weight of gasses, gravity, etc.) calculating buoyancy is. It is Constitution saving throw or gain one level of exhaustion.
suggested that you ignore buoyancy for most underwater Creatures with resistance or immunity to cold damage
adventures, but a few situations in which buoyancy is automatically succeed on this saving throw as do creatures
important will occasionally present themselves. As an that are naturally adapted to living in ice-cold water, such as a
example, the characters could use a light air balloon to escape polar bear or seal.
the deep ocean before their water breathing spell expires. The
characters might need to escape a quickly sinking ship and Cor a l
you need to know how deep below the surface the ship gets
before they finish looting everything in sight and bother to flee. Corals are tiny invertebrates that live in colonies that over
time create massive reefs. They can be very bright and strange
Simple Buoyancy. Buoyancy is the movement speed towards to look at and a few of the naturally occurring corals can
or away from the water’s surface that occurs at the beginning also be toxic, paralytic, or poisonous. Intelligent underwater
of each of a creature or object’s turns. The following table lists creatures could easily hide treasure and other valuables where
examples of buoyancy. Note that a negative speed means that contact with dangerous coral is inevitable or difficult to avoid.
the object sinks or moves a certain amount of feet towards the
bottom of the body of water and not the surface. Coral Bleaching. Coral is relatively easy to destroy with changes
in water temperature, hurricanes, bad luck, poison, pollution, etc.
Buoyancy Table This destruction, called bleaching, results from the coral (animal)
colony dying, which leaves behind sediment and the animal’s
Speed Example skeletons. A bleached coral colony usually takes 10 years to
60 ft. Water walk spell become healthy again.
40 ft. Lifting gas balloon
20 ft. Levitation spell Destroying Coral Reefs. A five-foot section of coral
10 ft. Air balloon reef can also be destroyed by characters or creatures.
0 ft. Most Living Creatures Each section has an AC of 15 and 20 hit points. Willful
- 10 ft Incapacitated Creature destruction of living coral reefs is considered a universal
- 30 ft. Sinking Ship taboo amongst all the aquatic humanoids, and if
- 50 ft. Sink cantrip witnessed, most will react with violence.
- 60 ft. Anchor
Sharp Coral Reef. Ghosts of Saltmarsh describes coral as a
Cold hazard that causes 1d6 slashing damage if a creature is forced
through or over coral.
Almost all bodies of water get colder the deeper you get, but
normal cold water should not directly cause cold damage, The following corals are variants that can be added to that
being no more of a threat than frigid water as explained in description or used by themselves. Creatures that try to avoid
Chapter 5 of the Dungeon Master’s Guide. contact with the coral can usually avoid these hazards entirely.
More Variety of Coral
Simple Coral Reef. Coral groups (reefs) of any significant
size, regardless of toxicity, are considered difficult terrain.
36 CHAPTER 3 | Difficulties and Oddities
Toxic (Irritant) Coral. Make a DC 10 Constitution saving Tides. In the natural world tides only exist because the
throw or suffer sharp irritating pains and disadvantage on moon’s gravity shifts the water level around the planet
all Dexterity saving throws and checks for 2d4 rounds. This causing a difference in sea level between low and high tides,
is a poison that can be cured and creatures immune to the sometimes as much as 15 feet. As the Dungeon Master, you
poisoned condition are immune to toxic coral. can make this relevant or not depending on your needs. If your
campaign world has multiple moons, then the tides could be
Toxic (Gill Cutter) Coral. This coral fills every five-foot cube rather confusing and hard to follow, or tides might not exist
adjacent to it with very fine particles that cut and irritate gills at all if there are no moons. Tides can force a timing element
(or lungs if a surface creature is breathing water). Make a DC in some adventure locations, since sea caves may only be
12 Constitution saving throw or have trouble breathing water accessible to air breathers during low tides, or the characters
and suffer disadvantage on all Strength and Constitution saving may need to wait for high tide before their boat can leave the
throws for the next 1d4 + 1 turns. river town’s dock.
Poisonous Coral. Make a DC 11 Constitution saving throw or Darkness, Light, and Vision
gain the poisoned condition.
Most flames, even magic or supernatural fire, will not produce
Paralytic Coral. Make a DC 10 Constitution saving throw or light or otherwise work underwater but a simple light cantrip
gain the paralyzed condition for 1d4 + 1 rounds. The target will. Ghosts of Saltmarsh defines ocean light zones, based on
can repeat the saving throw at the end of each of its turns, feet below the surface of the water, which helps to determine
ending the effect on itself on a success. how much light is available for creatures to see with. These
rules work well and they are reprinted (with only one small
Pearl’s Revenge. Make a DC 13 Constitution saving throw or variation) here.
take 1d6 poison damage and gain the paralyzed condition for
1d4 + 1 minutes. The target can repeat the Constitution saving Sunlight Zone. The sunlight zone extends from the water’s
throw at the end of each of its turns, ending the effect on itself surface to a depth of 650 feet. This area of the sea has the
on a success. same natural illumination conditions as above the water.
Currents and Tides Twilight Zone. The twilight zone is between the depths of
650 and 3,000 feet. When the sunlight zone above is bathed in
Currents. Ghosts of Saltmarsh describes how currents affect natural bright light. The twilight zone is filled with dim light.
surface travel and their speeds. That book describes subsurface If the sunlight zone is filled with dim light or darkness, the
currents as a Strength (Athletics) check against a DC (10 + number twilight zone is dark.
of miles per hour of current speed) and those that fail are moved
in the direction of the current 1d4 x 5 feet at the end of their Midnight Zone. Any depth below 3,000 feet is considered
turn. Ghosts of Saltmarsh simplifies current rules by stating that the midnight zone since no natural light from the surface
creatures with a swim speed are unaffected. These rules will work penetrates this deep. Note that the abyssal and hadal zones
fine for most situations but if you want a more nuanced version of are just as dark as the midnight zone of the ocean.
current or if the currents are strong enough to move swimming
creatures, then feel free to use the variant current rules. Obscuration. Water can range from clear to completely
obscured during storms, run-off, or dense algae blooms (or
Variant Current if the characters find themselves in sewage). There are some
natural and supernatural plants, creatures, and effects that
Currents or tides either cause movement through water to could illuminate the darkness, but this usually does not
count as if moving through difficult terrain or move a creature penetrate through obscuration. Note that a humanoid may
in the direction of the current. Currents are less of a hazard be blind when in dark or obscured water, but some marine
for creatures with a swim speed. The following table shows animals use other senses to detect living creatures (which
a suggested Strength (Athletics) check to ignore currents or functions as blindsight). A whale’s echolocation is a good
tides. A creature that is not fighting a current or tide (or one example of this.
that failed its Strength check) moves the displayed speed at
the end of its turn in the direction of the current. Swimming Phosphorescence. Various natural and supernatural
against the current for more than 10 minutes can eventually minerals and creatures emit light for a wide variety of reasons.
result in exhaustion, depending on the campaign. Riptides are When in doubt, assume that phosphorescent creatures and
an example of dangerous currents and they have been known objects found in nature emit bright light out to 10 feet, and dim
to drag humanoids away from a beach very quickly. light out to 20 feet. More importantly, these light sources will
be easy to locate in darkness and could easily be detected 200
Current/Tide Effect Table feet away depending on water quality and obscuration.
Current Speed Effect Effect Against Swim Speed Visibility, Obscuration, and Encounter Distance. The
Dungeon Master’s Guide’s encounter distance tables,
Gentle (5 ft.) Difficult Terrain None obscuration, and water visibility are reprinted here for your
convenience, but this table assumes that the characters and
Moderate (10 ft.) DC 8 or 10 ft. Difficult Terrain what they encounter are using the same sense (sight). If the
characters encounter sharks while exploring the sea, then
Strong (20 ft.) DC 11 or 20 ft. DC 8 or 10 ft. remember that the sharks will be aware of them before the
characters see the sharks.
Very Strong (30 ft.) DC 14 or 30 ft. DC 11 or 20 ft.
Dangerous (40+ ft.) DC 17 or 40+ ft. DC 14 or 30 ft.
CHAPTER 3 | Difficulties and Oddities 37
Underwater Encounter Distance Depth Damage to Items. Ghosts of Saltmarsh did introduce
an optional rule stating at which depths nonmagical items,
Water Visibility Obscuration Encounter Distance not designed to resist water depth, are destroyed. Items can
be designed to resist damage at greater depths, but there is
Clear water, bright light Clear 60 ft. only so much that can be done if the item is not enchanted
Clear water, dim light Light 30 ft. or protected from the depths. That table was modified and
Murky water or no light Heavy 10 ft. reprinted here.
Dead Zones (Hypoxia) Objects and Water Pressure
Some ocean locations, some as large as miles in radius, are Nonmagical Material Destructive Depth
dangerously low in oxygen, and creatures that can move avoid
these areas entirely. These regions can move and pop up Glass, crystal, ice 100 ft.
naturally or be created by arcane or divine means. Freshwater Wood, bone 500 ft.
sources can also be hypoxic for a variety of reasons. Water- Stone 2,000 ft.
breathing creatures will suffocate if they remain in these Iron, Steel 3,000 ft.
areas, and adventurers using spells like water breathing will Mithral 4,000 ft.
find themselves suffocating as well (see Suffocating, below). Adamantine 6,000 ft.
The new spell utility will help in these areas, and airy water
might work in these areas (up to the discretion of the DM). Bludgeoning Damage by Water Depth Variant
Deh y dr ation Crushing Depths. If you want crushing damage to affect a
creature as it gets deeper and deeper underwater, then any
Surface creatures will eventually dehydrate above the creature with gas-filled spaces (lungs, bladders, etc.) will be
waves but most aquatic and some amphibious creatures will extremely uncomfortable at 100 feet below the surface and
dehydrate much faster. This is usually not an issue unless an will be dead by about 1000 feet, regardless of swim speed,
aquatic creature is captured, gets lost, or has airbreathing cast unless immune to bludgeoning damage. The DM decides if
for a long duration. If this becomes important, then aquatic any creatures are immune to damage caused by this depth,
creatures must make a DC 10 Constitution saving throw for but anything remotely humanoid should not be. Certain types
every two hours spent outside of the water or they gain 1 level of monsters will be immune to bludgeoning damage caused by
of exhaustion. their depth underwater: constructs, elementals, oozes, slimes,
undead, and creatures at home in the deep ocean. Certain
Salt Water Ingestion (Hypernatremia). Besides animals spells, like control water or wall of force may also help to
found in the ocean and a few creatures that hunt there, prevent bludgeoning damage based on a creature’s depth.
natural creatures cannot drink salt water safely. A humanoid,
not native to saltwater, that drinks less than a cup of water Inescapable Depth Damage
is relatively safe but the easiest way to think of salt water
ingestion’s effects on the body is that it is negative water Depth (ft.) Effects
intake: the body dumps more water than it takes in in an
attempt to get rid of the salt. 200 1 bludgeoning damage per minute unless the creature
makes a DC 8 Constitution saving throw each minute.
A non-aquatic creature that drinks more than a cup of
saltwater needs to make a DC 15 Constitution saving throw or 300 1 bludgeoning damage per minute unless the creature
gain one level of exhaustion. This saving throw repeats itself makes a DC 10 Constitution saving throw each minute.
for every two cups of saltwater drank. To further complicate
things, consistently drinking salt water over time can lead to 400 1 bludgeoning damage per minute unless the creature
madness, but the effect and chances of madness are up to the makes a DC 13 Constitution saving throw each minute.
Dungeon Master.
500 1 bludgeoning damage per round unless the creature
Depth (Pressure) makes a DC 15 Constitution saving throw each round.
Damage to Creatures. Dungeons & Dragons, for the most part, 600 1 bludgeoning damage per round, unless the creature
ignores the crushing pressure of water and ignores it completely makes a DC 18 Constitution saving throw each round.
for creatures with a swim speed, and by ignoring this you can
often speed up gameplay at the cost of realism. In nature, over 700 1d6 bludgeoning damage per round, or half as much if
90% of sea creatures live in only the first 600 feet of the ocean the creature makes a DC 18 Constitution saving throw.
due to cold, pressure, and a steadily decreasing supply of oxygen Creatures make a saving throw each round at this depth.
as you go further down.
800 3d6 bludgeoning damage per round, or half as much if
If you do use the bludgeoning damage by water depth the creature makes a DC 20 Constitution saving throw.
variant rules, ignore all damage for sea creatures until Creatures make a saving throw each round at this depth.
they get below 600 feet deep. Life exists below 600 feet
but it is strange and may not survive being removed from 900 6d6 bludgeoning damage each round.
high pressure.
1000+ 12d6 bludgeoning damage each round.
38 CHAPTER 3 | Difficulties and Oddities
Direction Sense roll of 1 results in a misdiagnosis which forces disadvantage
on attempts to cure using an ability check until the disease is
Creatures born to water (those with a natural swim speed) will diagnosed correctly. Identifying a disease takes 1d10 minutes.
instinctively know which direction the surface is. Creatures
without a swim speed will usually not, and in darkness, Curing Diseases. Each of the diseases in this book will also
obscurement, or rough water will need to make a Wisdom list a DC to cure the disease using Wisdom (Medicine). The DM
(Insight) check to determine direction while underwater. This can feel free to adjust this number based on circumstances, lack
check is normally a DC 5, but the DM should increase this to of tools, supplies, etc. Curing a disease takes 1d20 hours.
10 for heavy obscurement, or 12 for darkness. If a character’s
sense of direction does not have an impact on game play, then Standard Diseases. There are three diseases found in the
this can and should be ignored. Direction becomes much more Dungeon Master’s Guide: cackle fever, sewer plague, and sight
relevant for unprepared characters running out of breath or rot. All three of these can be “acquired” during underwater
who find themselves disoriented in deep murky water. adventures, especially near civilization, stagnant water, or
sewage. If you are looking for additional diseases, then some
Diseases and Water natural (cholera) and fantasy (aqualung) diseases are explained
next. The real world name is listed in parentheses if the disease
A wide variety of very real and natural diseases and their is based on a real pathogen.
causes are associated with freshwater. Cholera is arguably the
most famous of natural diseases that are easily spread through Aqualung or Crusted Gill
water, but there are many more. In Dungeons & Dragons you
should treat a microscopic creature such as an amoeba or Aqualung is a fantasy disease of fluid build-up in the lungs, which
parasite as a disease to keep the gameplay from being bogged targets creatures that normally breathe only air but through
down. This means lesser restoration can cure maladies caused magical means breathe water for any length of time. Crusted Gill
by both. Some diseases cannot thrive in both saltwater and is a version of this disease that affects those who normally only
freshwater environments, but this work will ignore that. breathe water but breathe air through magical means.
No Diseased Condition Symptoms manifest 2d4 days after infection. This disease
causes a chronic cough, and cold-like symptoms, that go away
Dungeons & Dragons 5E does not have a diseased condition. This for a few days; the creature may then suddenly die if the disease
creates a situation where, as the Dungeon Master, you will have to remains untreated. A creature at risk of catching aqualung
decide if a creature that is immune to the poisoned condition is (crusted gill) must make a successful DC 11 Constitution
also immune to becoming diseased. In my campaigns some are, saving throw or become diseased. They will gain one level of
and some are not; it all comes down to why they are immune. exhaustion when the symptoms manifest but will otherwise feel
A wight is immune to the poisoned condition and I decided they are fine. If the disease is not cured after two weeks, they will need
also immune to becoming diseased. This is probably an easy call to make a DC 15 Constitution saving throw after each short or
to make. But is a master assassin, immune to poisons after a life of long rest or be reduced to 0 hit points and begin suffocating.
working with them, immune to disease? I decided that they are not. They will suffocate until they die, or the disease is cured.
These situations will come up in a campaign where diseases actually
occur and have to be dealt with by the player’s characters. A creature with aqualung (crusted gill) makes a DC 11
Constitution saving throw at the beginning of each day. If they
Disease Mechanics. As a simple gameplay mechanic, assign a succeed twice in a row, then they are no longer diseased.
percentage chance per day, that a character would “be at risk”
of catching a disease -- they make a saving throw or become
diseased. As a suggested guideline, a character in low-risk
situation (e.g., not swimming in a sewer) might only have a 1%
chance per day of being forced to make a disease saving throw
(see a particular disease for specifics). A character at moderate
risk (e.g., adventuring in a sewer but not swimming or injured
while in it) might have a 10% chance per day of being forced to
make a disease saving throw. Those with the highest risk would
be characters that were reduced to 0 hit points while swimming
in a sewer and it would be logical to make them make a disease
saving throw as an added bonus to nearly dying in filth. You can
adjust (or ignore) these percentage chances as you see fit.
Identifying Diseases. Each of the diseases in this book will
end with a section listing the DC to identify the disease using
Intelligence (Arcana), Intelligence (Nature), Wisdom (Medicine),
or Wisdom (Survival). A creature using Wisdom (Medicine)
can attempt to identify any disease normally. A character using
one of the other three skills does so at disadvantage. A natural
CHAPTER 3 | Difficulties and Oddities 39
Identifying. DC 12. Intelligence (Arcana) can be used to Cauliflower Scale (Lymphocystis)
identify this disease without disadvantage.
Medicine Curing. DC 15. A creature with proficiency in both Cauliflower scale is a disease that affects saltwater aquatic
Intelligence (Arcana) and Wisdom (Medicine) has advantage creatures, especially fish that are in poor water or kept as
on this check. pets. This disease starts as white spots, which then become
cauliflower-like bumps and growths that can be fatal to aquatic
Bat Brain (Brain-eating Amoeba) creatures, especially if it gets into the gills. This disease is very
infectious and a creature that breathes water within 15 feet of a
Bat brain is one of many creative names given for a humanoid diseased creature often catches cauliflower scale.
infected with a brain-eating amoeba. This disease is as rare as it
is fatal. It is contracted through swimming in freshwater rivers Symptoms manifest 2d6 days after infection. This disease
and lakes. This disease causes fever, then confusion, and finally causes lethargy, soft or lost scales, and difficulty breathing.
death, as the brain is slowly destroyed. Creatures at risk of cauliflower scale must make a successful
DC 15 Constitution saving throw or become diseased. After
Symptoms manifest 1d8 days after infection. A creature each long rest, a diseased creature must make a successful
at risk of catching bat brain must make a successful DC 10 DC 10 Constitution saving throw or have its Dexterity ability
Constitution saving throw or become diseased. An infected temporarily reduced by 2 until it is no longer diseased. This
victim will gain one level of exhaustion when symptoms appear, ability penalty can stack and if a creature reaches 0 Dexterity,
and this exhaustion cannot be cured until the disease is cured. they are reduced to 0 hit points and fail all death saving
1d4 days after the exhaustion occurs the creature will become throws unless they are cured of the disease, or die. A creature
confused, as per the confusion spell. 1d4 days after that the that makes two successful saving throws in a row is cured of
creature will be reduced to 0 hit points and automatically fail all the disease. A creature’s Dexterity is returned to normal if it
death saving throws unless the disease is cured. completes a long rest while no longer diseased.
Identify. DC 18.
Medicine Curing. DC 30. Identify. DC 12.
Medicine Curing. DC 9.
Bluerot
Cholera (Cholera)
This disease was reprinted and slightly altered from the disease
of the same name found in Ghosts of Saltmarsh. Bluerot can Cholera is an ancient diarrheal disease caused by poor
only infect humanoids. While afflicted with bluerot, a victim sanitation and tainted drinking water. It kills through
grows grotesque boils on their face and back. This disease is sudden dehydration. Most who are infected with cholera
carried by undead and creatures infected with the disease who recover naturally.
are using natural weapons like teeth and claws. The disease’s
boils manifest in 1d4 hours, causing the victim’s Constitution Symptoms manifest after a long rest. Creatures at risk of
and Charisma scores to decrease by 1d4 each, to a minimum catching cholera must make a successful DC 10 Constitution
of 3. This is quickly followed by a fever and tingling in the saving throw or become diseased and gain the poisoned
extremities. An infected creature is vulnerable to radiant condition. For the next twelve long rests, they must make a
damage and gains the ability to breathe underwater. successful DC 10 Constitution saving throw or gain a level of
exhaustion, which can be cured normally. After two successful
At the end of each long rest, an infected creature makes a saves (or after twelve long rests) they are cured of this disease.
DC 12 Constitution saving throw. On a success, the victim
regains 1 point of Constitution and 1 point of Charisma lost to Identify. DC 8.
the disease. If the infected creature regains all the points lost Medicine Curing. DC 8.
to the disease, it is cured. Other effects that raise the victim’s
ability scores do not cure the disease. On a failed saving Coral Scratch
throw, the victim takes 18 (4d8) necrotic damage as the boils
burst blue ooze and pus and spread. A creature reduced to 0 Sometimes a wound inflicted while underwater just won’t
hit points by this damage cannot regain hit points until the heal. This fantasy disease is often acquired after injuries
disease is cured, though it can be stabilized as normal. associated with coral, but any untreated wound can lead to
Identify. DC 10. coral scratch. Those suffering from coral scratch can only be
Medicine Curing. DC 15. A creature with proficiency in both healed with magic until the disease is cured. Possibly worst
of all, those suffering from coral scratch are easily infected by
Intelligence (Religion) and Wisdom (Medicine) has advantage other diseases and have disadvantage on any saving throw to
on this check. prevent or cure a disease other than coral scratch.
Symptoms manifest after a long rest. Creatures at risk of
catching coral must make a successful DC 10 Constitution
saving throw or become diseased and can only regain lost hit
points by magical means. This disease lasts for 2d6 days, at
which point it has run its course and the victim is cured. A
diseased creature also makes a DC 18 Constitution saving
throw each day and the disease is cured upon a success.
Identify. DC 5.
Medicine Curing. DC 15.
40 CHAPTER 3 | Difficulties and Oddities
Death Creaks (Scurvy) Gut Boil (E. Coli)
Death creaks is a disease resulting from a poor diet. This is Gut boil is often confused for food poisoning, and most will
usually only seen in prisoners or sailors who have not been on recover naturally. Some unlucky creatures will get bloody
dry land for over a month. The cure for this disease is fruits and diarrhea and vomiting that can lead to death. This disease is
vegetables, things that are difficult to come by while sailing. A caught by eating or drinking tainted food.
creature suffering from death creaks will begin to have loud
creaky joints after a few weeks if they continue to remain diseased. Symptoms manifest 1d4 days after infection. Creatures at risk of
catching gut boil must make a successful DC 9 Constitution saving
Symptoms manifest 2d4 days after infection. Creatures at throw or become diseased and gain the poisoned condition. After
risk of catching death creaks must make a successful DC 15 each long rest, they make a DC 9 Constitution saving throw. If they
Constitution saving throw or become diseased. A diseased succeed on two saving throws in a row, then they are cured. If they
creature will have to make another saving throw every week. fail three saving throws in a row, then they are reduced to 0 hit
Each failed saving throw results in a level of exhaustion that points and begin making death saving throws. If they survive their
cannot be cured until the disease is cured. Once the victim death saving throws, then they are cured.
gains three levels of exhaustion, the diseased creature has its
hit point maximum reduced to half. Once the victim gains six Identify. DC 8. Intelligence (Nature) can be used to identify this
levels of exhaustion the creature dies. This disease cannot be disease without disadvantage.
cured naturally by the body, but it is cured 2d3 days after the
victim’s diet includes fruits and vegetables. Medicine Curing. DC 11.
Identify. DC 5. Limb Rot (Flesh-eating Bacteria)
Medicine Curing. Impossible, automatic with access to fruits
Limb rot may occur after an injury, especially if the injury
and vegetables. is not cleaned or if the injury occurs in a filthy setting. This
disease poisons the blood and the flesh around the wound
Glass Stomach (Typhoid) begins to rot before the victim dies of septic shock.
Glass stomach is a disease caused by bacteria found in tainted Symptoms manifest 3d4 hours after injury. Creatures at risk
water, food, and freshwater. This disease causes severe of catching limb rot must make a successful DC 12 Constitution
stomach pains that make it almost impossible to stand up, saving throw or become diseased. After each short or long rest,
fever, and constipation. Victims will often display rose-colored they must make another successful Constitution saving throw
spots on their chest, but not always. or gain the poisoned condition and their maximum hit points
are reduced by 1d6 until this disease is cured. A creature that
Symptoms manifest 4d6 days after infection. Creatures at makes three saving throws in a row is cured of this disease.
risk of catching glass stomach must make a successful DC 11
Constitution saving throw or become diseased and gain the Identify. DC 12.
poisoned condition. A diseased creature must make a successful Medicine Curing. DC 12.
DC 13 Constitution saving throw every three days or gain one
level of exhaustion that can be cured normally. This disease is Marine Velvet
cured if the victim makes two successful saving throws in a row.
A creature that fails three saving throws in a row is reduced to 0 Marine velvet is a saltwater disease caused by a microscopic
hit points and must begin to make death saving throws. parasite. This parasite causes bleeding gills, exhaustion,
weakness, and finally death if marine velvet is not cured.
Identify. DC 10.
Medicine Curing. DC 10. Symptoms manifest 1d10 days after infection. This disease
which makes the gills appear highly inflamed is easy to spot
Green Spots but difficult to cure naturally. Creatures at risk of marine
velvet must make a successful DC 8 Constitution saving throw
Green spots is a fantasy disease that only affects amphibious and or become diseased. After each long rest, a diseased creature
aquatic humanoids. This disease can only be caught on dry land must make a successful DC 13 Constitution saving throw
after contact with an uncommon fungus that lives on grasses and or become diseased and have its Hit Dice reduced by 1 until
trees. This disease makes the skin crack and seep. It is not often the disease is cured. A creature that makes three successful
fatal, but very painful. saving throws in a row is no longer diseased.
Symptoms manifest 2d4 days after infection. Creatures at Identify. DC 5.
risk of catching green spots must make a successful DC 10 Medicine Curing. DC 15.
Constitution saving throw or become diseased. A diseased
creature will be diseased and have disadvantage on all saving
throws until cured. After each short or long rest they must
make a successful DC 8 Constitution saving throw or gain a
level of exhaustion that cannot be cured until the disease is
cured. A creature that spends its rest completely submerged
in water has advantage on this saving throw. This disease is
cured naturally after a total of three successful saving throws.
Identify. DC 10. A creature with a natural swim speed has
advantage on this skill check.
Medicine Curing. DC 10.
CHAPTER 3 | Difficulties and Oddities 41
Maztica’s Revenge (Legionnaires’) long this disease lasts and what minor effects, if any, it will
have on gameplay.
Maztica’s revenge occurs when tainted water is breathed in as
a mist or if a character is breathing fresh water. This disease Identify. DC 5 - 10.
resembles potent, and occasionally fatal, pneumonia. If untreated Medicine Curing. DC 10 - 15.
or uncured this disease eventually ends in death as the victim’s
lungs fill with fluid. Maztica’s revenge will produce a chronic Venereal Disease (Fatal). These are rarer but more serious
cough, shortness of breath, and a feeling of tightness in the chest. than venereal disease (annoyance). Each of these diseases
eventually kills the infected victim but this could take months
Symptoms manifest 2d4 days after infection. Creatures at or decades, depending on the Dungeon Master.
risk of catching Maztica’s revenge must make a successful
DC 10 Constitution saving throw or become diseased. A Symptoms manifest 2d20 days after infection. A creature
diseased creature must make a successful DC 8 Constitution at risk of catching venereal disease (fatal) must make a
saving throw every day or gain two levels of exhaustion. successful DC 13 Constitution saving throw or become
This exhaustion cannot be cured until the disease is cured. diseased. This disease lasts until cured or the infected victim
A creature that succeeds on a saving throw is cured. A dies. The Dungeon Master determines what happens to a
creature that fails three saving throws has 6 levels of creature as it slowly dies from this disease, but these diseases
exhaustion and is dead. usually take 2d20 months or 2d10 years to kill.
Identify. DC 13. Venereal Disease (Madness). These are rare and are just
Medicine Curing. DC 10. like venereal disease (fatal) but they slowly drive the infected
victim insane as well.
Sailor’s Regret (Giardia)
Symptoms manifest exactly like venereal disease (fatal), but
Sailor’s regret is a diarrheal disease caused by a parasite each month the victim suffers from the disease also requires
found in infected water, food, and soil. This disease is not as a successful DC 5 Wisdom saving throw or the creature
fatal as cholera but is sometimes mistaken for it. This disease gains an indefinite madness as described in the Dungeon
rarely kills healthy creatures, but it can last for weeks before Master’s Guide. Each additional month of being diseased
the body defeats it. increases the DC of the Wisdom saving throw by 1, with a
maximum DC of 15.
Symptoms manifest 1d4 weeks after infection. Creatures
at risk of catching sailor’s regret must make a successful DC Drowning (Suffocating)
9 Constitution saving throw or become diseased. A diseased
creature will be diseased for 2d4 weeks. Each day, they must Surface adventurers who seek to explore the watery depths
make a successful DC 8 Constitution saving throw or become fear one thing even more than the prospect of being eaten
exhausted. This exhaustion can be cured normally. The by sharks -- drowning. Drowning and suffocating should be
disease is cured naturally after its duration expires. treated the same in Dungeons & Dragons. To keep things
simple, use the existing suffocation rules as stated in the
Identify. DC 15. Dungeon Master’s Guide, which are reprinted here.
Medicine Curing. DC 8.
Suffocating. A creature can hold its breath for a number of
Variant Diseases - Venereal Diseases minutes equal to 1 + its Constitution modifier (minimum of 30
seconds). When a creature runs out of breath or is choking, it
Make sure you understand what you and your players can can survive for a number of rounds equal to its Constitution
handle before you include venereal (sexually transmitted) modifier (minimum of 1 round). At the start of its next turn, it
diseases in your campaign. I will avoid the graphic explanation drops to 0 hit points and is dying, and it can’t regain hit points
of most of them and boil venereal diseases down to three or be stabilized until it can breathe again.
categories: annoyance, eventually fatal, and madness. Each of
these categories has a wide variety of specific diseases with Air “Drowning.” A creature that only breathes water, like a
all sorts of entertaining and frightening names you should feel fish or an octopus, follows the rules for suffocating if removed
free to research on your own. Venereal diseases are not cured from water. Amphibious creatures that have issues with
by successful Constitution saving throws. A diseased creature extended stays in the air or water should have this mentioned
may live the rest of their life with a venereal disease, the in their statistics and descriptions.
duration could expire, they get cured with medicine or magic,
or they eventually die from the disease. Icebergs and Sea Ice
Venereal Disease (Annoyance) Icebergs are massive chunks of frozen fresh water (pieces
of glaciers) and sea ice is frozen sea water. This difference
These are the most common and most will go away will very rarely be important to you and your campaign, but
without treatment after a few weeks. But some of the icebergs extend far below the surface of the water and can
annoyance venereal diseases last forever unless cured by an function as temporary lairs to all manner of creatures. Sea
herbalist or magic. ice is rarely more than six feet thick, often covered in snow,
and treacherously slippery (movement on sea ice requires a
Symptoms manifest 1d12 days after infection. A creature successful DC 10 Dexterity (Acrobatics) check or fall prone).
at risk of catching venereal disease (annoyance) must
make a successful DC 13 Constitution saving throw or
become diseased. The Dungeon Master determines how
42 CHAPTER 3 | Difficulties and Oddities
CHAPTER 3 | Difficulties and Oddities 43
Swimming Water Hazards -- Supernatural
Surface Swimming. Swimming on the surface of the water Ancient Terrors. The deep oceans can hide almost anything
is easier than swimming under and through the water. As up to and beyond the size of a mountain. Those looking for
per the Dungeon Master’s Guide, after each hour of surface inspiration need only look to the work of H.P. Lovecraft. Various
swimming, a character must succeed on a DC 10 Constitution myths and legends also use the deep oceans as the prison of
saving throw or gain one level of exhaustion. A creature that the gods (the original Kraken and Cetus are good examples).
has a swimming speed can swim all day without penalty and To this end, I have designed most exit portals out of Carceri to
uses the normal forced march rules in the Player’s Handbook. dump travelers or escapees into the deep ocean. Something
escaping Carceri, that can survive cold and pressure, could
Subsurface Swimming. Creatures move the same speed either wander the deep indefinitely or eventually make its way
under the water as they do on the surface, for the alternative to the surface.
(more realistic version) would be crunchy and greatly delay
the game. What you should consider is that swimming under Antimagic Zones. These zones, sometimes referred to as dead
the water should be more exhausting than swimming on the magic zones, exist underwater but are thankfully as rare as they
surface, which is listed as a variant rule below. are dangerous to anyone traveling deep below the surface with
the aid of magic. Natural creatures pass through these areas
Subsurface Exhaustion Rules. Swimming through deep with no difficulty and do not normally avoid them, making them
water is like traveling at high altitudes. For a creature without undetectable and invisible. The spell antimagic field best describes
a swimming speed, each hour spent swimming at a depth what happens in these areas.
greater than 100 feet counts as 2 hours for determining
exhaustion. Swimming for an hour at a depth greater than Artifact Graveyards. There are more than a few ancient
200 feet counts as 4 hours. artifacts resting at the bottom of the deep ocean, tossed
there by the truly desperate who could find no other
Variant Subsurface Exhaustion means of disposal.
This variant rule can be used if you want a deadlier, more Deepened Darkness. Fantasy oceans contain patches of
realistic environmental challenge for creatures that attempt solid darkness, rumored to be older than the world, at depths
to swim under the surface for long periods. Creatures without greater than 3,000 feet. These patches consist of 2d100 5-foot
a swim speed or those unaided by magic or equivalent cubes joined together in roughly spherical shapes. Everything
devices become exhausted much faster than if they were at these depths avoids them, for deepened darkness radiates
swimming on the surface. Every ten minutes that a creature a strong aura of fear that causes any living creature within
swims through calm water they must make a successful DC 60 feet of it to flee (using the Dash action if possible) the
5 Strength (Athletics) check or gain 1 level of exhaustion. immediate area for a minute unless they succeed at a DC 18
After thirty minutes of swimming underwater, the check DC Wisdom saving throw. These patches of solid darkness drift
becomes 10, after an hour the DC becomes 15, and after 2 together with a swim speed of 5 feet. Every 5 points of radiant
hours the DC is now 20. The DM should either adjust the damage destroys a 5-foot-radius section, and any form of
DC of the saving throw or increase how often in an hour it sunlight makes the entire patch disintegrate.
must be made depending on current, situation, flotation aids, Any creature foolish enough to enter the darkness is in
encumbrance, armor, etc. difficult terrain regardless of swim speed, and those inside or
within 5 feet of any edge of deepened darkness are affected as
if in the area of effect of an Evard’s black tentacles (spell DC
18). This ancient danger is completely thoughtless and has no
known motivation.
Kraken’s Grave. These are fully explained in Ghosts
of Saltmarsh.
Lure Lights. These are fully explained in Ghosts
of Saltmarsh.
Powerful Aquatic Spellcasters. An enemy spellcaster’s dispel
magic or similar magic could quickly prove fatal depending on
how the characters are traveling and/or breathing water.
Sapping Snow. These are fully explained in Ghosts
of Saltmarsh.
44 CHAPTER 3 | Difficulties and Oddities
Undead Hordes Lacedon
The oceans have collected their fair share of undead over the The ghouls and ghasts in the previous table are not the aquatic
millennia and they form mindless herdes that shuffle along lacedon variety. They therefore do not have a swim speed and are
the bottom aimlessly. Even a few powerful forgotten undead shuffling along the bottom of the ocean in a horde.
creatures that are paralyzed in water rest at the bottom of the
ocean, waiting for something foolish enough to release them. Other Undead Horde Options. The following offer
Undead creatures that are not in hordes are either mobile, suggestions or questions to ask yourself if you want to flesh
intelligent, or powerful since many things at the bottom of the out an undead horde with more details.
sea can easily destroy and/or devour the undead.
Followers. Certain creatures may follow hordes, waiting to
Undead Horde Table. For the following table, each result devour stragglers that wander away from the pack. These
includes all the previous undead results. For example, if you could be aquatic versions of the carrion crawler, other
roll a 10, then the undead horde contains 10d20 skeletons, undead eaters, or normal swarms of fish that dart in among
10d20 zombies, and 5d20 ghouls. This table only shows the zombies picking morsels from the rotting corpses.
undead creatures that cannot swim or use their fly speed as
swim (see Chapter 7 for guidelines on undead using their fly Leaders. Each horde could be led by a powerful undead,
speed underwater). that for whatever reason has chosen to remain in the horde.
Examples are death knight, boneclaw, or sword wraiths (the
Undead Horde Composition latter two from Mordenkainen’s Tome of Foes)).
d20 Undead Encountered Skeletons and Zombies. Mix in a few non-generic skeletons
1-4 105 (10d20) skeletons and zombies (minotaur skeleton, ogre zombie).
5-8 105 (10d20) zombies
9-11 52 (5d20) ghouls (not lacedons) Undead Fish. See Appendix B.
12-13 26 (4d12) ghasts (not lacedons)
14-15 19 (3d12) drowned (see Ghosts of Saltmarsh) Why? What, if anything, keeps the horde together? Is it an
16-17 10 (3d6) wights object of evil, the ghost of a necromancer, an object of good
18 4 (1d8) vampire spawn used to keep the undead contained, or no reason at all?
19 2 (1d3) bodaks (see Volo’s Guide to Monsters)
20 Roll again, double all undead encountered rolls. This result
stacks if rolled again.
CHAPTER 3 | Difficulties and Oddities 45
CHAPTER 4:
UNDERWATER COMBAT
46 CHAPTER 4 | Underwater Combat
Existing Underwater Less Easy Underwater Combat
Combat Rules
Realism Over Speed. This version of 3D combat has
The Dungeon Master’s Guide lists the following rules for you track a new battle statistic, simply called “elevation.”
underwater combat: Assuming the Dungeon Master uses a battle board or other
two-dimensional “mat,” then each creature needs to have their
1. When making a melee weapon attack, a creature that elevation tracked above or below “0.” 0, in this system, would
doesn’t have a swimming speed has disadvantage on the then represent a reference plane that everything else is either
attack roll unless the weapon is a dagger, javelin, shorts- above or below. A creature at -10 would then be 10 feet below
word, spear, or trident. the battle map and a creature with a +10 would be 10 feet
above the battle map.
2. A ranged weapon attack automatically misses a target
beyond the weapon’s normal range. Even against a target Outside of a computer simulation, this is as simple as you can
within normal range, the attack roll has disadvantage unless make 3D combat. When all else fails, remember that Dungeons
the weapon is a crossbow, a net, or a weapon that is thrown & Dragons is primarily a roleplaying game and not a hardcore
like a javelin. combat simulation. The rest of this section assumes that the
Dungeon Master wants to use a realism over speed positional
3. Creatures fully immersed in water have resistance to fire system that tracks elevation of each target in combat. This gets
damage. a bit tricky if a creature is directly under or over whatever they
are attacking. I suggest you stack d6 in this case. For example, a
Do Not Stack Fire Resistance locathah is being attacked by two sahuagin; one below, and one
above it. Stack three dice of different colors and the locathah
I suggest that you do not rule that a creature is immune to fire would simply be the die in the middle.
damage if they are already resistant to fire when outside of water. If
you allow fire resistance to stack into fire immunity while a creature In two-dimensional combat, a Medium creature can be
is underwater, then you will have an issue with characters wanting attacked by 8 other Medium creatures armed with shortswords.
to wander into thermal vents or ignore superheated water, etc. In 3D combat, a Medium creature can be attacked by 26 other
A ring of fire resistance should not allow a character to play with Medium creatures armed with shortswords. Being surrounded
magma bubbling up from an underwater vent. is always a bad thing, but being surrounded in 3D is much
worse. The end of this chapter shows an example of being
Three-Dimensional surrounded in 3D.
Combat Underwater
Determining Encounter Direction. In a 3D space, an
Three-dimensional (3D) combat allows creatures to fight each encounter can start above, below, behind, or some other angle
other in new and interesting ways that you normally don’t see other than directly in front or to the side of the characters.
on a battlefield unless you are running a battle with flying You can use the following table to determine encounter
dragons, charging knights, and a burrowing bulette all at the direction for random encounters that occur underwater (or
same time. Intelligent creatures fighting in 3D will attempt any other 3D space).
to either encircle an enemy or prevent their enemy from
encircling them. They can choose to fight near the surface Three-Dimensional Encounter Direction
which reduces the threat from above, deep in a coral reef, or
with their backs to a wall or cliff. d12 Direction
1 Encounter is to the front of the characters.
Easy Underwater Combat 2 Encounter is to the left of the characters.
3 Encounter is to the right of the characters.
Speed Over Realism. Three-dimensional combat can be 4 Encounter is to the front and above the characters.
completely ignored since Dungeons & Dragons is not built to 5 Encounter is to the left and above the characters.
simulate that level of realism. In this case, conduct combat 6 Encounter is to the right and above the characters.
as you normally would, and the 3D elements can just be 7 Encounter is to the front and below the characters.
explained or used as part of your story or the setting of an 8 Encounter is to the left and below the characters.
underwater battle. 9 Encounter is to the right and below the characters.
10 Encounter is behind the characters.
11 Encounter is below the characters.
12 Encounter is above the characters.
Diagonal Movement. Every other diagonal move in 3D costs
an extra 5 feet of movement.
Diagonal Reach. A reach of 5 feet threatens everything that
can surround a creature (see the diagrams at the end of this
chapter). After this simple rule, think of reach as the radius of
a sphere surrounding a creature.
CHAPTER 4 | Underwater Combat 47
Feats Underwater Skills Underwater
The following feats will not work (or not work as well) if the Creatures with a swim speed will find that most of their skills
character or creature using it doesn’t have swimming speed can be used underwater as normal. Creatures without a swim
(or freedom of movement). This list of feats only involves the speed will discover that almost everything is more difficult
feats listed in the Player’s Handbook. How a feat will function underwater (when in doubt, most skills are at disadvantage).
underwater from any other source is up to your discretion. Anyone attempting to do much of anything underwater while
wearing heavy armor will face a variety of issues as stated in
Charger. This feat will not function at all if used underwater Chapter 5. You will find yourself making a few “house rules” if
without a swim speed or freedom of movement. you are running an extensive underwater campaign; so many, in
fact, that I won’t list them all out. But here are a few issues you
Elemental Adept (Fire). This feat will not ignore fire will run into.
resistance if used against a target underwater, but the damage
improvement will be unchanged. Acrobatics. This skill can be used in so many ways
that you will have to evaluate each use of this skill when
Keen Mind. This feat grants advantage on a creature’s used underwater.
attempt to determine which direction the water’s surface is.
Knowledge of true north will not be automatic (and mostly Athletics. Some uses of athletics will not be at disadvantage,
useless) underwater. even without a swim speed, but the opposite is also true, and a
swim speed does not automatically remove all disadvantages.
Mobile. This feat will not function at all if used underwater A creature without a swim speed that gets into a Strength
without swim speed or freedom of movement. contest with a creature that has a swim speed will have
disadvantage underwater; but bending an iron rod, even when
Sharp Shooter. This feat will not function underwater underwater, should not be any easier or more difficult than
regardless of swim speed or the use of freedom of movement. doing the same in an area filled with air.
A possible exception to this is if the creature is firing from
within the effect of an airy water spell, and the target is also Initiative. Remember that initiative is really a Dexterity check
inside that area. and a creature with disadvantage with their checks will,
therefore have disadvantage on their initiative rolls. This will
Variant 3D Surrounded Penalty Unnecessary be relevant when a character, in heavy armor at the bottom of
the sea, is rolling initiative (see Chapter 5).
Being surrounded in 3D results in being attacked by 26 opponents if
they are the same size as you. This is usually quite dangerous in its Stealth. Stealth should work normally unless a creature
own right. You can rule that some or all of them have advantage on without a swim speed is trying to “swim stealthily,” which will
their attack rolls, but I have found this to be unnecessary since the be at disadvantage or impossible.
target is in very serious trouble to begin with.
Tracking. Tracking should be at disadvantage underwater
regardless of swim speed unless the tracker is an aquatic or
amphibious creature not relying on sight in order to track.
In most situations, tracking someone underwater using only
one’s sense of sight should be impossible.
Intelligence- and Charisma-based Skills. The skills
associated with Intelligence and Charisma usually function
normally underwater.
48 CHAPTER 4 | Underwater Combat
SURROUNDED in 3D
Elevation +0 feet
Elevation +5 feet Elevation -5 feet
CHAPTER 4 | Underwater Combat 49
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