Dive Tables

1
Dive Tables

• The purpose of this presentation is to review the
  use of the NAUI Dive Tables.
• It is best if you have a copy of the NAUI Dive
  Tables while you work through this presentation
• You can print out a copy of the tables at the My
  Scuba Tutor section of our web site
  www.diveunderwaterworld.com.

2
Definitions To Know

• Actual Dive Time (ADT) Time calculated from the
  beginning of the descent to the return to the
  surface, less the safety stop.
• Maximum Dive Time (MDT) The maximum time you
  can spend at a given depth without the need to
  decompress.
• Depth The maximum depth reached during the
  dive.
• Repetitive Dive Any subsequent dive within 24
  hours of a previous dive.
• Repetitive Dive Group A letter designation
  indicating the amount of nitrogen remaining in a
  divers body from the previous dive or dives.
• Repetitive Nitrogen Time (RNT) The amount of
  nitrogen remaining in the body expressed in
  minutes. This time must be counted as part of the
  current dive. It is like a penalty. You do not
  get to dive it but you must count it.

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Definitions To Know (continued)

• Total Nitrogen Time (TNT) Total amount of
  nitrogen in a divers body. This includes Actual
  Dive Time Plus Residual Dive Time i.e. ADT RNT
  TNT
• Adjusted Maximum Dive Time (AMDT) Maximum dive
  time adjusted for previous dives by deducting
  residual dive time.
• Surface Interval Time (SIT) Time between dives.
  Must be at least 10 minutes to count as surface
  interval.
• Safety Stop Three minute stop at 15 feet. Not
  mandatory but highly recommended.
• Decompression Stop Mandatory stop. Usually
  performed at 15 feet, but deeper stops could be
  required
• Planned Depth (PD) Planned depth of next dive.
• Planned Depth Plus (PD) Planned depth of next
  dive plus 10 feet.

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Residual NitrogenTo properly use dive tables and
dive computers, you must understand the concept
of residual nitrogen.

• Residual nitrogen reduces your time limits for
  any given depth on your next dive. Each
  successive dive will add additional residual
  nitrogen and reduce the no decompression time
  allowed on the next dive. Note how the nitrogen
  levels drop during the surface intervals but
  build from that point during the next dive.

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Dive Table OverviewThe NAUI Dive Tables use a
Letter Group designation to express the amount of
residual nitrogen in your body.

• The letters range from A to L.

6
Dive Table TermsThe following apply to the NAUI
Dive Tables

• Maximum Dive Time (MDT) Shown as a number inside
  a circle inside a square.
• Decompression Stop Shown as a number above a blue
  box indicating depth of stop.

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Dive Table RulesYou must understand the
following dive table rules completely.

• Ascend no faster than 30 feet per minute.
• Use exact or next greater number listed for your
  depth.
• Use exact or next greater number listed for your
  time.

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Dive Table Rules continuedYou must understand
the following dive table rules completely.

• Use the deepest depth you reach during your dive.
• Always make your deepest dive first.
• Dives shallower than 40 feet are planned as 40
  feet.

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Dive Table Rules continuedYou must understand
the following dive table rules completely.

• Surface interval time must be at least 10
  minutes.
• Use the next greater dive time if it was cold or
  strenuous.
• Avoid dives that take you to the no-decompression
  limit.

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Dive Table OrganizationThe NAUI dive tables are
composed of three tables.

• Table 1 End of Dive Letter Group (for the
  current dive 60 feet for 40 minutes). Start
  where it says Start (Left side of right table.)
  Go down the depth column to 60 feet, then across
  the time row to 40 minutes. The go down from 40
  feet to find the letter group indicating the
  amount of nitrogen in you body.

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Review on Dive Table 1What have you learned so
far?

• List the Group Letters for the following dive
  profiles
• If you do a dive to 18 meters (60 feet) for 42
  minutes.
• If you do a dive to 12 meters (40 feet) for 88
  minutes.
• If you do a dive to 36 meters (120 feet) for 9
  minutes.
• Answers H, I, D

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Dive Table OrganizationThe NAUI dive tables are
composed of three tables.

• Table 2 Surface Interval Time (SIT) Table. Start
  with the repetitive group from the end of your
  first dive and continue down that column
  (following the arrows) until you find the block
  of time that your surface interval fits into.
  Then follow that row to your left to find your
  new letter group.

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Review on Dive Table 2What have you learned so
far?

• List the new Group Letters for the following
  Surface Interval Times
• You have a group letter of I and your SIT is 2
  hours and 36 minutes.
• You have a group letter of C and your SIT is 3
  hours.
• You have a group letter of G and your SIT is 42
  minutes.
• Answers E, B, F

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Dive Table OrganizationThe NAUI dive tables are
composed of three tables.

• Table 3 Repetitive Dive Timetable. Continue
  across the new groups row until you reach the
  column indicating the depth of your repetitive
  dive. The note your AMDT and RNT. The footnote at
  the bottom of the chart shows which is which.

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Review on Dive Table 3What have you learned so
far? Answer the following questions.

• 1. If you have a beginning Letter Group of D and
  you want to dive to 18 meters (60 feet), your
  AMDT is _____ minutes.
• 2. If you have a new letter group of B and you
  want to dive to 27 meters (90 feet), your AMDT is
  _____ minutes.
• 3. If you have a beginning letter group of G, you
  can dive to 24 meters (80 feet) for _____
  minutes.
• 4. If you have a beginning Letter Group of E and
  you dive to 17 meters (57 feet), your RNT is
  _____ minutes.
• 5. If you have a beginning Letter Group of G and
  you dive to 11 meters (37 feet), your RNT is
  _____ minutes.
• 6. If you have a beginning Letter Group of C and
  you dive to 20 meters (67 feet) for 22 minutes,
  your TNT is _____ minutes.
• 7. If you have a beginning Letter Group of D and
  you dive to 16.2 meters (54 feet) for 18 minutes,
  your TNT is _____ minutes.
• Answers 31, 18, 0, 30, 73, 37, 42

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Dive Planning WorksheetYou must systematically
keep track of your dive information when working
with NAUI Dive Tables.

• Planning your dive.
• Finding your letter group.
• Recording your SIT and finding your new group
  letter.
• Planning your repetitive dive.
• Recording your repetitive dive.
• Always diagram your dive.

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Review on Dive TablesReview the following
problems using your planning worksheet. If you do
not have one, you can print it from My Tutor.
1. Your first dive of the day was to 20 meters
(66 feet). You descended at 940, surfaced at
1019, and completed a 3-minute precautionary
decompression stop (ADT36). Your second dive
was to 14 meters (46 feet). You descended at
1232, surfaced at 113, and completed a 3-minute
precautionary decompression stop (ADT38). Your
third dive was to 12 meters (40 feet). You
descended at 243, surfaced at 326, and
completed a 3-minute precautionary decompression
stop (ADT40). 2. Your first dive of the second
day of your trip was to 24 meters (80 feet). You
descended at 835, surfaced at 858, and
completed a 3-minute precautionary decompression
stop (ADT20). Your SIT was 2 hours and 46
minutes. Your second dive was to 16 meters (52.5
feet) for 36 minutes including your precautionary
decompression stop (ADT33). You surfaced at
1220. Your third dive was to 10 meters (33
feet). You descended at 310, surfaced at 410,
and completed a 3-minute precautionary
decompression stop (ADT57).
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Maximizing Underwater TimeYou cam maximize your
dive time by adjusting your SIT, your depth, or
your ADT.

• Limiting your dive time means you absorb less
  nitrogen during that dive.
• Increasing your surface interval allows you to
  outgas more nitrogen, reducing your residual
  nitrogen times.
• Limiting your depth reduces your nitrogen uptake
  during that dive.

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Special RulesThere are a number procedures you
must learn to handle special situations. Discuss
these with your instructor.

• Decompression diving.
• Precautionary decompression stops.
• Required decompression.
• Omitted decompression.
• Cold or strenuous dives.
• Flying after diving.
• Altitude diving.