PADI IDC Exam Example Questions and Answers

Note these are not official PADI questions but are similar to the ones that you would be expected to know, they have been created by myself when Staffing IDCs to give to give to students when they wanted more example / sample exam and test questions. There are plenty of multiple choice test questions in your open water manuals and in the Knowledge Development Workbooks if you have a copy of them. I would also recommend looking at the dive master exams again.

Here is a selection of exam questions and answers that you should tackle in exam conditions to test your dive knowledge. Remember dive theory wont take up 100% of your time when you are a PADI Dive Instructor (OWSI) but you need to know it 100% and actively encourage people to learn more about it.

A good teaching tip is to reference what your students have learned in class when they are in the water, for example when you talk about descending, say something like "remember we learned about water pressure and the effects it has on our body today in the classroom? well when we descent the increasing weight of the water will have the following effects on us...............".

Example PADI IDC and IE Exam Questions

Some are common dive knowledge and some are multiple choice questions (Metric and Imperial). Use either metric or imperial numbers when figuring out your answers. Some RDP questions are listed twice (metric and imperial versions).

How many confined water sessions and open water sessions are there in an Open Water course? 
5 and 4

To Participate in DLD experience the participant must do what ?
Read / Sign a Liability release and assumption of risk form
What is the normal full pressure of a recreational scuba tank ?
200 bar / 3000 PSI (there are 15 psi per bar) 
For your information: Most countries apart from the US use Bar as a measurement of pressure for tanks

What is the pressure of a tank that began with 200 Bar and was slowly opened and left for hours until it was empty ?  
1 Bar (most people think 0 Bar, but unless you live in a vacuum it's the normal atmospheric pressure at sea level which is 1 Bar)

 Which program has a Open water Dive Ration of 10:1   ? 
Skin Diver

According to Henry's law, what causes something to absorb more gases into solution?
Salty water
PressureDensity
Lung Capacity

What are the two basic parts of a regulator called?
The two basic parts of a regulator are called the first and second stage.

According to Charles' law, what increases as the temperature of a gas increases?
Density
Speed 
Pressure
Volume

At what depth will you reach 2ATM of pressure?
33ft or 10m

To reduce the risk of decompression sickness (DCS – nitrogen bubbles blocking blood circulation/flow in your body after a dive):
a) ascend (go up) to a shallower depth if you feel dizzy and thirsty
b) have your tank filled only at a dive center you trust.
c) breathe more slowly than normal using Nitrox
d) make a safety stop at 5 metres (15 feet) at the end of each dive.e) use Nitrox / Enriched Air on every dive

You make two dives in one day and you are flying home on a commercial plane. What is the minimum time you have to wait before you can go on the plane?
a) 36 hours
b) 24 hours
c) You do not have to wait.
d) 18 hours

Certified DMs must complete how many DSD Internships to be qualified to conduct them ?  
4 DSD Programs
What is Confined water ?
look this one up but its basically a pool or a body of water with pool like conditions
Underwater most sounds seem to come from where ? 
overhead

In the unlikely event that you are in an out-of-air situation (OOA), and you are close to your dive buddy, the best thing to do is to:
a) make a controlled emergency swimming ascent (CESA – swim up to the surface saying the ah-h-h sound).
b) buddy breathe (share a single regulator with your buddy).
c) switch to your buddy's alternate air source - Remember to do the out of air sign.
d) panic and rush to the surface 
e) use the air in your BCD.

note: if you answered d then this is obviously wrong and dangerous

How do you avoid CNS Oxygen Toxicity
Don't exceed an oxygen PP of 1.4 ata

What percentage of Air is Oxygen ?
21%

What are Heat Exhaustion Signs & Symptoms?
Weak, rapid breathing, weak rapid pulse, profuse sweating, skin cool and clammy, nausea

What is a Visual Inspection  ?
Checks for damage and wear / allows for maintenance and lubrication – is a dive industry standard

How does a  transducer work and where would you find one?’
Varying an electrical current depending on the pressure exerted on it – Dive Computers have transducers in them

When do waves break ?
Waves Break when approaching the shore – When the depth is the same height as the wave

What is the most common reason for Cylinders slipping in nylon tank bands?
Due to adjusting the band while it was dry

The rate at which a theoretical tissue absorbs and releases nitrogen is called its?
Halftime.

Can you can rely on a Haldanean Deco model?
Only as far as it has been shown to work in test and by field experience

What are waves caused by?
Wind

What causes currents in the bodies of water around the world?
Wind and the earth's rotation.

What causes Tides?
Gravitational pull of the Earth and the Moon.

did you know that - Pressure Gradient is greater at Altitude that's why different procedures must be adopted over 300m.

What are the Signs and Symptoms of Oxygen Toxicity?
VENTID - Don't know what that means ? carry on reading your books :)
Once you get your Instructor Manual look through the Standards section (at the front) and familiarise yourself with its layout and content, look up stuff like ages for courses, depths etc

Imagine you were diving from a dive boat (common in most dive resorts) and get caught in a strong current at the surface. Should you?
a) Descend (go down) and try to swim against the current near the bottom.
b) Make yourself buoyant / float, then signal the boat for help, and try to swim against the current.
c) Make yourself positively buoyant and float, signal for help, rest and wait for the boat to pick you up.d) Try to swim against the current by staying just below the surface.

Most scuba diving injuries caused by fish and aquatic animals happen because:
a) the marine animal is trying to protect itself and is scared of you
b) the animal is aggressive and wants to hurt you.
c) the animal wants to mate with you.
d) the animal thinks you are dinner!

Decompression Sickness types and general areas affected?
DCS1 Pain Only 
DCS2 Nervous System

Divers who act strangely or foolishly at depth may start acting normal again if they:
a) breathe slowly and deeply.
b) ascend (go up) to a shallower depth.
c) signal their buddy for help.
d) All of the above.

You are likely to increase the risk of decompression sickness (DCS) if:
a) you do not look after your equipment.
b) you are tired, cold, sick, thirsty or overweight.
c) you dive in poor visibility, strong moving water, and rough seas.
d) All of the above.
e) a and c only

 
METRIC — RDP table or eRDP: You dive to 17 metres for 23 minutes. After a 30 minute surface interval, you plan to dive to 16 metres. What is the maximum allowable time for the second dive?
a) 10 minutes
b) 61 minutes
c) 51 minutes
d) 27 minutes

METRIC — RDP table or eRDP: You are a newly qualified instructor and you are planning to make two dives. The first dive is to 21 metres for 30 minutes, and the second dive is to 15 metres for 36 minutes. How long would you have to stay on the surface between dives (minimum surface interval) to do these two dives safely?
a) 9 minutes
b) 1 hour and 4 minutes
c) 29 minutes
d) Instructors do not need to wait between dives

METRIC — RDP table or eRDP: You dive to 17 metres for 44 minutes. After a one hour surface interval you do a second dive to 17 metres. Losing track of time, you notice your bottom time is now 37 minutes. What should you do?
a) Ascend (go up) right away to 5 metres and stay there for 8 minutes before going to the surface.
b) Go to the surface right away and contact the nearest recompression chamber.
c) Ascend (go up) right away to 5 metres and stay there for 3 minutes before going to the surface then drink lots of fizzy drinks on the boat.
d) Ascend (go up) to 3 metres and stay there until you use up your air.

IMPERIAL — RDP table or eRDP: You dive to 59 feet for 22 minutes. After a 30 minute surface interval, you plan to dive to 50 feet. What is the maximum allowable time for the second dive?
a) 10 minutes
b) 61 minutes
c) 29 minutes
d) 59 minutes

IMPERIAL — RDP table or eRDP: You are a newly qualified instructor and you are planning to make two dives. The first dive is to 21 metres for 30 minutes, and the second dive is to 15 metres for 36 minutes. How long would you have to stay on the surface between dives (minimum surface interval) to do these two dives safely?
a) 49 minutes
b) 1 hour and 4 minutes
c) 2 hour and 32 minutes
d) Instructors do not need to wait between dives

IMPERIAL — RDP table or eRDP: You dive to 17 metres for 44 minutes. After a one hour surface interval you do a second dive to 17 metres. Losing track of time, you notice your bottom time is now 37 minutes. What should you do?
a) Ascend (go up) right away to 5 metres and stay there for 8 minutes before going to the surface.
b) Go to the surface right away and contact the nearest recompression chamber.
c) Ascend (go up) right away to 5 metres and stay there for 3 minutes before going to the surface then drink lots of fizzy drinks on the boat
d) Ascend (go up) to 3 metres and stay there until you use up your air.

If you descend and then you find your ears or sinuses hurt while you are going down, it normally means:
a) your air spaces are equalized (cleared).
b) your mask strap is too tight.
c) you are feeling a squeeze and need to equalize.
d) your mask is too small.
e) hurting ears are fine and you should get used to it as a diver.

You should not even consider diving if you currently have a cold or are suffering from any allergies because:
a) you will get your Doctor in trouble for clearing you to dive.
b) you may become tired or seasick easily.
c) you may not be able to equalize pressure in your body air spaces.
d) you will use your air up too fast.
e) you may become unconscious (dazed, out cold) without warning.

If you hold your breath while scuba diving can:
a) damage your lungs
b) preserve your air so you can dive for longer
c) push air into the blood stream and chest area.
d) give yourself life threatening injuries.
e) a, c and d

You should skip breath when
a) you want to preserve your air
b) your buddy is better at preserving his or her air
c) tank refils are expensive in your area
d) never

Heat Stroke –What do you do ?  
Cool diver and get him to medical aid station

What are the conditions caused by the failure of body's temp maintenance systems?
Hypothermia and heat stroke

A forceful Valsalva and delayed middle ear equalisation can cause what ? 
Ear - Round window rupture

What is the most important rule in scuba diving? - if you don't know this give up now :)
a) diving is great at getting rid of hangovers
b) Always perform a pre dive safety check.
c) Establish positive buoyancy and relax when at the surface.
d) Never dive alone.
e) Breathe continuously and never hold your breath.f) find cool people to dive with.

If you are having to work too hard and find it difficult to breathe underwater, you should:
a) get to the surface quickly by inflating your BCD.
b) stop your diving and rest, hold onto something for support if possible.
c) swim right away to your buddy and signal for help.
d) do a controlled emergency swimming ascent (CESA - swimming up to the surface giving it the the ahhhh sound).
e) try a different hobby like ping pong
f) dont let anyone see as its embarrasing to suck at diving

  Divers are most affected by CONDUCTION. Least affected by RADIATION.

You know you are properly weighted for diving if you:
a) are the first to the reef from the boat.
b) sink slowly holding a normal breath of air and an empty BCD.
c) float at eye level holding a normal breath of air with an empty BCD.
d) float at neck level with your BCD about half full and you are holding a normal breath of air.
e) desend as slowly as the largest person in your dive party. 

If you and your dive buddy were separated / couldn't find each other underwater what would you generally do?
a) Check your air and tailor your search pattern depending on how much you have left.
b) Find your buddy's bubbles and follow the bubbles to find your buddy.
c) Go up right away, wait a minute and then go back down underwater.
d) Search for a minute underwater and then go up to find your buddy.
e) Go to the surface right away and get out of the water. 

Imagine you feel a mild current at the start of your dive. How should you begin this dive?
a) Drink lots of coffee and fluids as your in for a tough dive
b) Dive against or into the current.
c) Never dive with a current.
d) Dive in the direction of the current (taking it easy :) )e) Dive across the current. 

 Shallow Water Blackout caused by Hypocapnia due to a falling oxygen partial pressure.

Best time to dive ? 
Slack tide after a high tide

 Eustachian tube leads to the middle ear (from the throat)

What is the water pressure at 34m in Fresh water (.97) ? 
Absolute and Ambient  4.3 ATA / Gauge 3.3 ATM

You should be able to answer these simple open water questions without the answers, if you cannot then re-read the open water manual, you should also be able to explain why the wrong answers are not correct to someone that thinks that they are correct!

Still want more questions? good, have a look here for more general knowledge and some sample PADI IDC / IE quiz / exam questions and answers

I am a great believer on the fact that you don't really know something until you can teach someone else about that subject, think about describing water pressure on ears or air consumption at depth to a student. Practice this often with fellow students, start by saying ‘teach me about…………' and then ask each other questions, it's the best way to learn.

Now you are at the end, hopefully you will have a better understanding of Dive Theory, if you can answer all your PADI quizzes and exams and complete the Knowledge development workbooks and your ‘mock' exams in the Instructor Manual then you will be fine on the theory, if you are worried about the practical skills and demonstrations / teaching presentations then get help from your local dive center and perhaps you want to consider doing a pre-idc preparation courses that most Course Directors offer.

 

Good Luck, Dive safe and look after yourself and your future divers, you always remember your first certification and I hope you get as much out of it as we did.

Dive Theory - The Recreational Dive Planner (RDP)

You have got a shiny new Dive Computer so you can skip this step, erm no you can't, you need to know this part inside out. For your own safety and the safety of your students. Not to mention that as a dive professional you should set a good example and carry either the RDP or Wheel in your BCD pocket as a back up and also enforcing good diving practices. Unfortunately you can not take the erdpml underwater!

Compartments.

Where different tissues in the body release / absorb nitrogen at different rates.  Different parts of the body absorb and release nitrogen at different rates.  Blood and fat absorbs nitrogen easier and faster than muscle and bone.   Because of these different TISSUES, a decompression model has what we call THEORETICAL TISSUES or COMPARTMENTS.  Compartments are a way to measure / identify how fast or slow our body (and body tissues) absorb and release nitrogen.  FAST COMPARTMENT (blood) = absorb and release nitrogen fastSLOW COMPARTMENT (muscle and bone) = absorb and release nitrogen slowly.

Many dive computers now use the RGBM model which uses theoretical compartments as follows
2.5 mins Blood
5 min Brain
10 mins – 40 mins Spinal Cord
40 mins – 120 mins Skin
120 mins – 480 mins Muscle
480 mins + Joints etc

Halftimes

The rate at which the compartment absorbs / releases half capacity of nitrogen Each compartment has a halftime for the rate at which it absorbs and releases nitrogen A halftime is the time, in minutes, that it takes for a certain compartment to reach halfway from its initial tissue pressure to full pressure, (saturation), at a new depth.

Compartments “on gas” and “off gas” at the same rate. Hence the controlling compartment for surface intervals of the RDP is the 60 min compartment which takes 6 hours ,(6 x 60 mins) to reach it’s M value. This compartment also takes 6 hours to empty, there for a a repetitive dive is a dive made within 6 hours of a previous dive, allowing for the 60 min compartment to completely empty.

FAST (tissue) COMPARTMENT (gas washout) = SHORTER HALFTIME
SLOW (tissue) COMPARTMENT (gas washout) = LONGER HALFTIME

1.         After 5 minutes the compartment will go to halfway (half full)
2.         After 5 minutes more the half from the first 20 minutes will half again
3.         This halfing can only happen 6 times exponentially. The new compartment will always be considered saturated (full) when it reaches approx 98.6 percent.  To make it easier the tissue pressure can be expressed or called ‘metres'.

PRESSURE IN HALFTIME

COMPARTMENTS

1          Halftime (50%) in 18m = 9m of pressure (18 x 0.5)
2          Halftime (75%) in 18m = 13.5m of pressure (18 x 0.75)
3          Halftime (87.5%) in 18m = 15.75m of pressure (18 x 0.875)
4          Halftime (93.6%) in 18m = 16.8m of pressure (18 x 0.936)
5          Halftime (96.9%) in 18m = 17.4m of pressure (18 x 0.969)
6          Halftime (100%) in 18m = 18.0m of pressure

Example:
A 5-minute halftime compartment will have how much tissue pressure 5 minutes after taken from the surface to 18 metres depth?
After 5 minutes the compartment will go half way to saturation.
So if this is a 18m compartment, then half of 18m is 9m.
Answer = 9m of pressure 
To continue: After 10 minutes the pressure will go half way again.
Half the remaining 9m.  Half of 9m = 4.5m.
Add this to the first 9m (9m+4.5m) = 13.5m

M-VALUE

The M-Value is the MAXIMUM TISSUE PRESSURE (nitrogen level) that is allowed to be left in the body after a dive.
The faster the compartment, the shorter halftime.
The slower the compartment, the lower the M-value
The higher the M-value, the more nitrogen it is allowed to have upon surfacing.
The M-value represents what does and does not result in DCS.
These M-values are the A-Z on the RDP
A = a low level (low pressure) of nitrogen
Z = a high level (high pressure) of nitrogen.
At 12m our halftimes are shorter, so we can have a high M-value

E.g.  We can dive at 12m for 147 minutes = Z (M-value) 
At 30m our halftimes are longer so we have a low M-value
E.g.  We can dive at 30m for only 20 minutes = N (M-value) 
The compartment that reaches its M-value first, is called the CONTROLLING COMPARTMENT

WHY THE US NAVY (USN) TABLE WAS ‘STANDARD' FOR RECREATIONAL DIVING
The USN table was developed mainly for military decompression diving, but they became almost the standard in recreational diving until the mid-1980s for several reasons.   Before computers, developing a table was a difficult process that had to be calculated by hand.  Few outside the Navy had the information or the ability to produce tables.  Many early sport divers began as military divers, bringing the USN tables with them.  The USN tables were widely available in the public domain, allowing publishers to reproduce and re-arrange them.  Though they weren't ideal for recreational divers, they could be relied upon when following accepted conservative diving practices.

THE RDP TODAY - Dive Theory - RDP / Dive Tables

The RDP, as we know it today, was developed in 1987 and tested in 1988 by Dr. Raymond E Rogers (a PADI dive master) working with DSAT (Diving Science And Technology).

DIFFERENCES BETWEEN US NAVY TABLES & RDP

RDP	USN Table
NO–DECOMPRESSION (NO STOP)	STAGE DECOMPRESSION USE
14 Compartments	6 Compartments
60 minute surface credit	120 minute surface credit
Halftimes have faster gas washout	Halftimes have slower gas washout
6 hours to be clean of nitrogen	12 hours to be clean of nitrogen
Designed for multiple dives a day with a shorter surface interval (recreational diver)	Designed for limited dives a day with a longer surface interval (military use)
Longer bottom time on repetitive dives	Shorter bottom time on repetitive dives

HOW COMPUTERS COMPARE WITH EACH OTHER & THE RDP WITH RESPECT TO SURFACE INTERVAL & M-VALUES

Computers at times give longer no-decompression limits, because they 
Calculate the dive exactly
Eliminate unnecessary rounding (that you would do when using a table)

SPENCER LIMITS, EE WASHOUT

EE = ‘Exponential-Exponential'
Approximately the same M-value as the RDP
All compartments release theoretical nitrogen at the surface at their underwater halftime rate, as compared to the RDP, which releases theoretical nitrogen at the 60-minute rate for all compartments of 60 minutes or faster.  This washout means these computers can permit dives beyond what has been tested to work.  E.g.  3 dives to 40m in a row for 10 minutes each with only 30 minutes between them.  This washout is not a problem if divers avoid multiple deep dives with short surface intervals (generally not recommended whether using a computer or not)

SPENCER LIMITS, 60-MINUTE WASHOUT

Based on data for RDP
At the surface, all compartments 60 minutes and faster washout at 60 minute rate, all slower compartments wash out at their underwater halftime rate (like the RDP).
Dives very similar to what the RDP model allows.

BUHLMANN LIMITS, EE WASHOUT

Further reduced M-values (based on the work of Dr. Buhlmann) All compartments washout at their underwater halftime rate With reduced M-values repetitive dives similar to what the RDP supports, though repetitive deep dives with short surface intervals may still permit dives beyond what has been tested to work.  Spencer limits, 60-minute washout and Buhlmann limits, EE washout seem to be the most popular types of computers.

GENERAL RULES FOR USING THE RDP

PRESSURE GROUPS ON THE RDP

Letters (pressure groups) CANNOT be swapped (are not interchangeable) between the RDP, USN or any other tables.
You can link pressure groups between different versions of the RDP, such as the wheel and the enriched air 32% and 36% recreational dive planner.

COLD WATER DIVING

When planning a dive in cold water or under conditions that may be strenuous (difficult), plan the dive as if the depth is 4m deeper than actual.

REPETITIVE DIVES

Plan repetitive (2nd or 3rd) dives so each next dive is to the same, or a shallower depth.
Don't follow a dive with a deeper dive.
Max depth of 30m on repetitive dives
Plan your deepest dive first

LIMIT MAXIMUM DEPTHS TO TRAINING & EXPERIENCE

Discover Scuba Diver / Scuba Diver – 12m
Open Water Diver – 18m
Advanced Open Water / divers greater training and experience – 30m
40m is the maximum training depth for Deep Specialty Course
The 42m on the RDP is for emergency purposes only

SPECIAL RULES FOR SURFACING PRESSURE GROUPS

When planning 3 or more dives in a day:
If the ending pressure group after any dive is W or X the minimum surface interval between all next dives is 1 hour.
If the ending pressure group is Y or Z the minimum surface interval between all next dives is 3 hours Limit following dives to 30m / 100 feet or shallower

SAFETY STOPS

Make a safety stop for 3 minutes at 5m after every dive (recommended).  The time at a safety stop need not be added to the bottom time of the dive.
Always make a safety stop:
After any dive to 30m or deeper
Anytime you will surface within 3 pressure groups of your NDL
When a dive is made to any limit (black box) of the RDP

IN-WATER RECOMPRESSION

In-water recompression – treating DCI by putting the diver back underwater shouldn't be attempted.
Recompression takes a long time and requires oxygen and often drug therapy.
Normally the required resources aren't available at a dive site and incomplete recompression will usually make the diver even worse.

EMERGENCY DECOMPRESSION

An emergency decompression stop for 8 minutes at 5m must be made if a no-decompression limit is accidentally exceeded by 5 minutes or less.  Upon surfacing the diver must stay out of the water for at least 6 hours before making another dive.
If a no-decompression limit is exceeded by more than 5 minutes a 5m emergency decompression stop of no less than 15 minutes is needed (air supply permitting).  Upon surfacing the diver must remain out of the water for at least 24 hours before making another dive.

DEEPER THAN 40M?

If you accidentally go below 40m immediately ascend (18m per minute) to 5m and make an emergency decompression stop for 8 minutes. 
If the no-decompression limit for 40m is NOT exceeded by more  than  5 minutes.  Do not dive again for at least 6 hours.

MISSED DECOMPRESSION STOP

If you accidentally miss a required decompression stop and have already surfaced and exited the water, remain out of the water and stop diving for 24 hours and breath pure (100%) oxygen if available

DIVING AT ALTITUDE

Using the RDP at altitudes 300m above sea level requires the use of special training and procedures.
Add 4% to the depth for every 300m above sea level.  Conversion table is on page 15 in PADI Adventures In Diving manual.
Rule of thumb:- Subtract 0.035atm for each 300 m of altitude.
A lake is at 1800 m altitude.  A lift bag with 1 Lt of air inside is released from a depth of 10 m.  What will the air volume be on reaching the surface?
1800
--------  =  6 x 0.035  =  0.21atm  - 1 atm  = 0.79atm
300

Pressure at 10m  = 1atm + 0.79atm = 1.79atm
1.79 x 1 Lt of air
---------------------- = 2.26 lts
0.79

FLYING AFTER DIVING
A minimum surface interval of 12 hours is required before flying.  
If you make daily, multiple repetitive dives for several days, or make dives that require decompression stops a minimum surface interval of 18 hours is required before flying.

Recreational Dive Planning (RDP) - The Wheel revision

Single Depth Dives

Use the book that came with your wheel for practise and revision 
1st dive.            26 metres for 20 minutes

Side 1.
Put the white arrow onto 26 on the outer edge.
Put the yellow arrow onto 20.
Read the yellow PG index where it cuts the 26m curved line.  = PG = ‘L'.
Surface time 30 minutes.
Side 2.
Locate ‘L'.
Rotate wheel until 30 lines up with ‘L'.
Top of the white curved line = New PG ‘G'.
2nd dive.           24 metres for 15 minutes.
Side 1.
Move the white index until ‘G' touches the 24m curve.
Move the yellow arrow onto 15.
Read the yellow PG index where it cuts the 24m curved line.  = PG = ‘Q'.

3rd dive.            18 metres for 25 minutes.

Find the minimum surface interval? 
Side 1.
Line the Yellow index until it touches the NDL cross hatch of the 18m curve

Move the White index until 25 mins lines up with the Yellow arrow, follow the 18 m curve up and check which White letter touches the 18 m curve. In this case it is the letter L  

Side 2
Find the Q and then rotate until the top of the white line touches the bottom cross hatch for the L
Minimum Surface Interval time = 21 mins.

RECREATIONAL DIVE PLANNING ERDPML VERSION.

1st dive 26m for 20 mins
Turn on and make sure ERDPML is in metric mode.
Select ‘Dive Planning’ mode and press ENTER.
Multilevel ? Select NO, First Dive ? press YES
Enter Depth………Enter 26 m
NDL 27mins
Enter Actual Bottom Time……….20 mins
Pressure Group after dive “L”
Press Enter
Enter Surface Interval Time…………..30 mins and press enter 
PG after SI = G……press enter

2nd DIVE 24m for 15 mins
Enter Depth………Enter 24 m……press enter
Adjusted No Decompression Time ANDL 16 mins…….press enter
Enter Actual Bottom Time………..15 mins…….press enter
ERDPML should beep and flash warning of a safety stop, ( RULE 2 )
Press Enter ……Ending Pressure Group R

3rd DIVE 18m for 25 mins
FIND THE MINIMUM SURFACE INTERVAL
Select Surface Interval Mode….press Enter
First Dive Y/N……Enter No
Pressure Group end of Dive…….press number 7,3 times for R press enter
Enter Depth 2…….Enter 18m and press enter
ANDL = 50 mins……..press enter
Enter ABT2……….enter 25 mins……press enter
ERDPML should beep and flash warning of a safety stop,( RULE 2 ) press enter
Minimum Surface Interval = 30 mins

Multi-level Dives (Up to 3 different depth levels)

1st level 28 metres for 10 minutes.
As before.
Side 1.
Put the white arrow onto 28 on the outer edge.
Put the yellow arrow onto 10.
Read the yellow PG index where it cuts the 28m curved line.  = PG = ‘E'.
(Note maximum multi-level (ML) time is the same as the NDL time = 23 minutes).
By following the 28m curve read at the centre maximum 2nd depth is 20 metres.

2nd depth 18 metres for 15 minutes.
18 metres is below 20 so it is OK to continue.
Move the white index until ‘E' touches the 18m curve.
Move the yellow arrow onto 15.
Read the yellow PG index where it cuts the 18m curved line.  = PG = ‘M'.
(Note maximum multi-level (ML) time is 28 minutes).
By following the 18m curve read at the centre maximum 3rd depth is 12 metres.

3rd depth 10 metres for 20 minutes.
10 metres is below 12 so it is OK to continue.
Move the white index until ‘M' touches the 10m curve.
Move the yellow arrow onto 20.
Read the yellow PG index where it cuts the 10m curved line.  = PG = ‘Q'.
(Note maximum multi-level (ML) time is 131 minutes).

Multi-level Dives ERDPML (Up to 3 different depth levels)

1st level 28 meters for 10 mins

As before, turn on, select mode, Dive Planning, press enter.
Multi level Y/N?......press YES
First Dive Y/N?.......press Yes
Enter level………press 28m……..press enter
NDL = 23 mins…..press enter
Enter ABT………..enter 10 mins and press enter…PG = E after first level

2nd level 18 meters for 15 mins
Press enter
Enter level 2………enter 18m, press enter, ML = 29 mins……press enter.
Enter ABT……enter 15 mins and press enter
PG after level 2 = M……

3rd level 10meters for 20 mins
Press enter….
Enter level 3…..10 m and press enter…..ML = 130 mins….press enter
Enter ABT…….enter 20 mins….press enter
Pressure group after dive = Q
PLEASE NOTE THAT USING THE WHEEL THE NEXT DEEPEST DEPTH IS PRINTED ON THE ACTUAL WHEEL IN A YELLOW BOX AT THE CENTER OF THE WHEEL.
WHEN USING THE ERDPML YOU WILL HAVE TO ACCESS INSTRUCTIONS FOR USE BOOKLET PAGE 82.

Recreational Dive Planners (wheel, table, erdp)

1.         They are designed for recreational diving and use conservative limits to minimise bubble formation, even at levels that do not cause DCS.
2.         They were tested using Doppler technology not available when the Navy tables were developed.
3.         They contain more surface interval times for higher precision.
4.         They base surface interval elimination on half time that creates a realistic credit for surface intervals.
5.         The wheel / erdpml makes it possible to calculate multi-level dive times by giving credit for slower nitrogen uptake in shallow water.
6.         The wheel / erdpml allows the diver to more closely calculate time and depth profiles.

RDP Summary

Decompression theory is based on models and doesn't have any relationship with real people (but it's the best model we have so we rely on it)
All tables and computers are based on Haldanean decompression model, which are mathematical extrapolations.
First tables produced in 1906.
Different parts of the body absorb and release dissolved nitrogen at different rates.(different compartments / different halftimes)
Haldane's original model had 5 compartments, from 5 to 75 minutes, modern versions have 14 or more, ranging from 3 to more than 600 minutes.
Each compartment has a halftime for the rate at which it absorbs and releases nitrogen.
Halftime = the time in minutes, for a particular compartment to go halfway from its beginning tissue pressure to saturation at a new depth, in exponential progression.
After 6 halftimes the compartment is considered saturated (actually 98.6%).
The difference between the dissolved nitrogen pressure and the surrounding pressure (whether ascending or descending) is called the pressure gradient.
M-value = the maximum tissue pressure allowed in the compartment when surfacing to prevent exceeding acceptable gradients.  (in our diving we only use the one that applies at the surface).
The M-value is calculated for surfacing at sea level, at an altitude higher than 300m the gradient may be too high unless you use altitude diving procedures.
The US Navy used Haldane's tables and revised them periodically to meet changing needs.
The 1950 (current) US Navy tables had 2 important differences from the original Haldane model.
6 compartments were used with 120 minutes halftimes.
Surface interval credit added all divers in the previous 24 hours and were treated as one dive.
US Navy table were used until the mid 1980's because:-
Many early sport divers were ex Military.
The US table were available to the public.
They could be relied on.
The original US Navy tables designed its surface interval credit on the worst case 120 minutes halftime.  This is why, worst case, it take 12 hours to be clean.
In the mid 1980's Raymond Rogers a Divemaster recognised that the Navy tables might not be ideal for recreational diving.
The 120 minute surface interval credit was excessive for no-decompression dives.
The Navy tables were designed for males, fit and between 20 and 40 and not females etc.
Doppler ultrasound flow meters had not come into being.
During tests in 1987 and 1988 Rogers established:-
The 60 minute surface interval credit concept.
Extensive testing of multilevel diving.
Included a broader demographic test subjects.
The test were based on limiting Doppler detectable bubbles.
Multi-day testing successfully tested the RDP making 4 dives daily for 6 days.
Spencer 60 minute washout and Buhlmann EE washout seem to be the most popular types of computers

Skills and Environment

Waves

1.Capillary waves – very small.
2. Storm waves – large – 30 m +.
3. Wind causes waves.
4. Only the wave shape or energy moves.
5. The effects of the wave stops at a depth of 45m.
6. Waves are measured by height and length.
7. When a wave is as deep as its height, bottom friction slows the forward speed, it bunches up becomes higher / steeper then breaks.
8. They cause a ripple affect on the sand running parallel to the shore (handy for natural navigation)

Tides

1. Twice daily.
2. Tides result from gravitational interaction between the earth, sun and moon.  Also topographical features.
3. The moon has most effect.
4. Tidal wave results from seismic activity.

Currents

1.Coriolis effect – Northern Hemisphere – deflections to the right.
2.As a result water piles up in the middle of the pacific ocean.
3.Northern hemisphere trade winds blow from the NE to SW.
4.Currents negligible at depths of 190m.
5.Wind energy and the coriolis effect drives the ocean currents.
6. Northern hemisphere major ocean currents flow clockwise.
7.Southern hemisphere major ocean currents flow counter-clockwise.
8. The major current in the southern hemisphere turn: counterclockwise
9. Best time to diving: slack tide when high tides peaks
10. Currents are caused by wind and the earth's rotation
11. Tides are caused by: the gravitational interaction of the earth, moon and sun

Compass

1. Trust your compass: even if you think you are going to the wrong direction
2. Triangle: 120 degrees for each corner
3. Reciprocal heading on a compass means: 180 degrees from the initial heading
* Natural navigation, directional information: plants, animals, bottom composition (rocks, sand ripples…), light and shadow

Altitude Diving

1. RDP can be used using the Theoretical Depth at Altitude Chart from: 300 meters to 3000 meters
2. Ascent rate when diving in Altitude is: 9 meters per minute
3. If you want to do two dives in different altitude: the first must be in the highest altitude.
4. To use the RDP: only with special procedures
5. Altitude Diving: Capillary depth gauge
6. Planning an altitude dive: actual depths must converted to theoretical depths to find the pressure group
7. Special procedures:
- Nitrogen narcosis may occur at shallower depth
- The ambient atmospheric pressure at altitude is less than at sea level
- Actual depths must be converted to theoretical depths to find no decompression limits on the RDP

General information

1 CPR compression ratio for Adult, child and infant: 30/2
2 Use a lifting device, weight recommended: 4-7 kilos
3 Maximum depth for recreational diving is: 40m
4 CESA: must keep all the equipment in place, surfacing while emitting a continuous AHH sound
5 Recommendation for Safety Stops: at the end of every dives
6 Night Dives: one dive light but recommended that each divers 2 lights
7 Marine life injuries includes: respiratory depression or arrest, local swelling,
inflammation, severe pain, numbness, paralysis, cardiac arrest
8 Alternate air source: should be placed between the chin and the corners of your rib cage
9 Difference between DCS and Lung overexpansion is: DCS tends to appear a few hours after, Lung overexpansion upon surfacing

Boat Terminology

Front of the Boat is called the Bow
Back of the boat is called the Stern
Left is Port
Right is Starboard
Head is the Toilets
Galley is the Kitchen

 

 

Wind

Winward is towards the boat
Leeward is away from the boat (so if your feeling a bit unwell best stand Leeward)