Dive Tables - Practice Questions - Fish-Tail.com

Dive Tables - Practice Questions

Question 1

4 : 20 <>

70’ 60’ 40’
65 mins
30 mins 35 mins
DIVE 3
DIVE 1 DIVE 2

Find the minimum surface interval required to carry out DIVE 3

Answer 1

F 4 : 20 B H 1:07 >F K

70’ 60’ 44 40’ 69
30 mins 65 mins
35 mins
DIVE 1 RNT = 61
RNT = 11 ADT = 65
ADT = 35 TNT = 126
TNT = 46
DIVE 3
DIVE 2

Steps for answering question 1

1. Calculate the End of Dive Letter Group for dive 1 using Table 1.

Look up 70 ft dive for 30 mins - the diver ends dive 1 as an F diver.

2. Calculate the letter group after the surface interval between dive 1 and dive 2 using
Table 2 - Surface Interval Time Table.

Look down the ÒFÓ column until you find the time period surrounding 4 hrs 20
mins ( between 3:58 and 7:05 ) read to the left and you find you start dive 2 as a
B diver.

3. Check if dive 2 is possible using Table 3 - Repetitive Dive Table.

Where the B diver row meets the 60 ft column there are 2 numbers. The RED
number is the Adjusted Maximum Dive Time ( AMDT ) - the time the diver can
actually spend at 60 ft. In this case 44 mins - our plan is to spend 35 mins on the
dive - so it is a good plan.

4. Calculate the Total Nitrogen Time ( TNT ) for dive 2.

The BLUE number in table 3 where the B diver row and 60 ft column meet is the
Residual Nitrogen Time ( RNT ) 11 mins - add this to the Actual Dive Time (
ADT ) 35 mins to get the TNT - 46 mins.

5. Calculate the End of Dive Letter Group for dive 2 using Table 2.

Look up 60 ft dive for 46 mins ( the TNT from step 5 ). Dive 2 ends as a H diver

6. Calculate the minimum surface interval between dive 2 and 3 ( work the tables
backwards )

Start at Table 3 with the details of dive 3 to find the letter group that allows the
diver to complete a 40 ft dive for 65 mins. Look UP the 40 ft column for the first
AMDT ( red number ) that is greater than or equal to 65 mins. This is 69 mins
read across to find the letter group - an F diver.

Move to Table 2 and check where the F diver meets the H diver ( from step 5 ).
This is between time 1:07 and 1:41 - the MINIMUM surface interval is 1 Hr and
07 mins.

7. Complete the plan by adding the RNT of 61 mins ( F diver / 40 ft dive in Table 3 ) to
the ADT - 65 mins to get a TNT 126 mins. Table 1 - 40 ft dive for 126 mins the final
letter group is K

Question 2 2:53 <>
60’ 50’
90’ 25 mins 40 mins
21 mins
DIVE 2 DIVE 3
DIVE 1

Answer 2

G 2:53 D H 1:42 E J

90’ 60’ 31 50’ 42
21 mins 40 mins
25 mins
DIVE 1 RNT = 38
RNT = 24 ADT = 40
ADT = 25 TNT = 78
TNT = 49
DIVE 3
DIVE 2

Remember : if the actual depth or time is not on the tables use the next
greater value.

Question 3

A buddy pair are planning 3 dives.

The first dive will be to 83 ft for 15 mins. After spending 2 hrs and 30 mins
on the surface they will make a second dive to 55 ft for 23 mins.

The final dive will be to 45 ft for 35 mins.

Calculate the minimum surface interval between dives 2 and 3 to allow the
pair to complete their final dive.

Answer 3

E 2:30 C G 1:16 E J

83’ 55’ 38 45’ 42
15 mins 35 mins
23 mins
DIVE 1 RNT = 38
RNT = 17 ADT = 35
ADT = 23 TNT = 73
TNT = 40
DIVE 3
DIVE 2

Note : it is easier to calculate dive plans if you draw the profiles.