IDC Guide

General Skills & Environment


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)


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.


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


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

PADI IDC Skills: and Environment – Skills

The Basics

The SKILLS section of a PADI IDC Skills and Environment exam can be divided into easy and familiar subjects: Open Water course skills, PADI Programs and questions from other PADI IDC Exam topics.

How it works

Open Water Course

Favourite questions focus mostly on two skills:
Emergency Weight Drop, where it’s important that the weight is dropped away from the body to avoid snagging on equipment and CESA where it’s important to keep all equipment in place, particularly the regulator.


PADI Programs

Questions regarding the benefit of Discover Local Diving, where it’s beneficial to be introduced to a new dive site by local guides, and ReActivate, where divers can refresh the skills that are relevant to their individual needs and experience levels.


Other IDC Exam topics

You are likely to find questions from the Physiology Exam. For example there might be questions about Stomach (or Diaphragm) breathing. Also questions from Equipment Exam. For example, the importance of doing a weight check on the surface if you switch from steel cylinder to aluminium or vice versa.

PADI IDC Skills: and Environment – The Environment

The Basics

The Environment part of the IDC Skills and Environment exam is mostly made up of natural behaviours in the ocean, and techniques of how to handle different situations.
This might help.

Natural Behaviours in the ocean

You’ll find questions about rip currents, where trapped water between obstacles flows seaward creating a danger. Also questions about wind causing waves, or the behaviour of the Coriolis effect where major ocean currents flow clockwise in the northern hemisphere and anti or counter clockwise in the southern hemisphere. You might get questions about local tides, particularly that it’s often better to dive at high slack tide.


How to handle different situations

This area covers the suggestion that you should stand sideways against surf when entering the water and use ripples in the sand as a navigation aid. It also covers search patterns and what headings to use when swimming a square

PADI IDC Skills: and Environment – First Aid

The Basics

Even though this is a PADI IDC Skills and the Environment section, you’ll find a lot of questions about Rescue and First Aid

This might help.

You will find questions that emphasise that you need to establish buoyancy any time that you meet a diver in trouble at the surface, and There are also questions about the need to give 100 pct. Oxygen to victims suspected of suffering from DCS.

First Aid
The First Aid questions range from a reminder that one person CPR is 30:2 through to Marine stings, where it’s advised to rinse the sting in the same water and to treat jelly fish stings with vinegar.

Also questions about the need for a suspected drowning victim to get medical advise, despite feeling well.

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


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

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