1. Dive Tables
Planning dives safely

2. Objectives Describe the function of the dive tables.
Define common dive tables terminology and concepts.
Plan repetitive dives not requiring stage decompression.
Determine contingency mandatory decompression stops.

3. Main points
Dive tables aid in planning safe dives by setting depth and time limits
Must understand the terminology
Must adhere to the rules
Recreational diving does not involve decompression stops
Decompression stops are listed for contingences purposes
We utilize computer but understand the tables are still key to safe diving

4. Terminology Dive Profile Actual Dive Time (ADT) Depth or max depth
statement of depth and time
70 feet for 40 minutes
Actual Dive Time (ADT)
Surface to surface time
Depth or max depth
Deepest point of dive no matter how brief the time spent there.
Maximum Dive Time (MDT)
Maximum time you can spend on a dive to a given depth without requiring a mandatory decompression stop.

5. Terminology End-of-Dive Letter Group Surface Interval (SIT) New Group
Symbol representing amount of excess nitrogen in your body at the end of the dive.
Surface Interval (SIT)
Time on surface between dives.
During the SIT you are getting rid of some excess nitrogen (off-gassing) and therefore your letter group, will change.
New Group
Letter group at the end of the SIT
Repetitive Dive
Any dive made within 24 hours of a preceding dive.

6. Terminology Residual Nitrogen Time (RNT) Adjusted Maximum Dive Time
Excess Nitrogen in your body after a dive
Represented by your new group at the end of the SIT
Adjusted Maximum Dive Time
The maximum dive time for a repetitive dive to a given depth.
Total Nitrogen Time (TNT)
Represents total nitrogen load in your body at the end of a dive
Determined by combining RNT +ADT = TNT

7. Terminology Safety Stop Mandatory Decompression Stop (Deco stop)
Voluntary stop at the end of every dive
Facilitates outgassing of Nitrogen
Reduces the likelihood of bubble formation
Mandatory Decompression Stop (Deco stop)
Required stop at 15 feet whenever MDT or AMDT has been exceeded
Beyond the training of recreational diving

8. Rules for Using the NAUI Tables
Rate of ascent
1/2 foot per second or slower.
Depth
Use exact or next greatest number.
Time
Use exact or next greatest number
Dive sequence
Deep to shallow recommended
During the dive
For any rep. dive
SIT
Minimum recommended : 1hr
Minimum recognized : 10min
Keep activity to a minimum
Drink water

9. Rules for Using the NAUI Tables
Sport Diving Maximum Depth 130ft
Altitude Diving
Special training/tables required when diving at altitudes above 1000 feet.
Flying after diving
1 recreational dive: 12 hours
Multiple recreational dives: 18hrs
Multiple dive/multiple days: 24hrs
Mandatory deco stop: 24hrs
Long, cold, strenuous dive
Use next greater TNT

10. Safety stops Maintain depth of 15ft for 3mins
Minimal activity throughout the stop.
Deep stops: (different schools of thought)
initial 1-minute stop at a depth equal to ½ the Max depth,
followed by a 3-minute stop at a depth of 15 feet.
For example, on a dive to 100 feet of seawater (FSW),
make a 1-minute stop at a depth of approximately 50 feet,
followed by 3-minute stop at a depth of approximately 15 feet.

11. Stage Decompression Diving
Dives that require a mandatory decompression stop.
Beyond the realm of sport diving
However you should have contingency information and be familiar with the minimal emergency procedures in case the maximum recreational dive time is exceeded.
Omitted Decompression
Missed mandatory decompression stop and no symptoms
Rest, drink fluids, and watch for signs of DCS.
Do not re-enter water for at least 24 hours.
If signs/symptoms of DCS are present treat for DCS

13. Walking through the table
Find depth column
Find dive time rows
Find max time for 40ft, 60ft, 100ft
Find max time for 44ft, 55ft, 81ft
Finding letter groups
60ft/30min
70ft/36mins
81ft/22mins

14. Table 2 (SIT Times) Finding your next letter group Letter group E
SIT for 1hr
SIT for 1hr 20mins
SIT for 2hrs
Letter group H
SIT for 30mins
SIT for 1hr 8mins
3hrs

15. Table 3: Repetitive dive table
Starting off with a new letter group
Find your planned Max Depth
Top number is your RNT
Bottom number is your AMDT
Examples
E diver: what's your AMDT for
40ft
60ft
75ft

16. Lets get complicated Dive 1 Dive 2 60ft/40mins Letter group? 2hr SIT
New letter group?
Dive 2
MDT for 50ft?
SIT time for a 30min dive at 50ft?
If SIT=2hrs; then dive = 50ft/30mins
what’s my new letter group? (TNT calculation)

17. Mandatory Decompression Stops
Found in table 1
Boxes to the right of the circled numbers
Top number
Indicates ADT requiring Mandatory Deco stoop
Bottom number
# minutes that must be spent at 15 feet
Example
A diver has a dive schedule of 100 feet/23 minutes
The diver must spend 5 minutes at 15 feet
Note that any time from 22:01 – 25:00 requires this stop

18. Mandatory Decompression Stops
The actual stage decompression tables for air diving are extensive. The information provided here is for contingency purposes only.
Stage decompression diving requires extensive training and equipment, and is beyond the realm of recreational diving.

19. Before the Dive
Prior to entering the water for any dive you must ask yourself, and answer, the following questions:
How much excess Nitrogen, if any, do I have left in my body from previous dives?
Residual Nitrogen Time or RNT
What will be the maximum depth of my dive?
What is my time limit for the planned depth of the dive?

20. Post Dive
After the dive you must ask yourself, and answer, the following questions:
What was the maximum depth of my dive?
How long did I stay under water?
Actual Dive Time (ADT).
What is the total Nitrogen load in my body?
Total Nitrogen Time (TNT).
What is my end of dive letter group?