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  • Tracy Gunn

Dive Skills and the Environment IDC Dive Theory

Updated: Feb 12

Dive Skills and the Environment can feel overwhelming as it seems to cover many different subjects, but it can be broken down into three main topics.

  • The Environment You Dive In

  • Courses

  • Health and Safety

The information and exams included here are to help you understand that vast and diverse world of diving and to give you a head start for your IE.






What do we know more about?

The moon or the ocean???

Oceans cover 71% of the Earth’s surface with an average depth of 3800mt/12450ft

3% is fresh water, with ¾ frozen in Polar ice caps. Another 20% is groundwater.

Most of our knowledge about the seafloor is limited to depths of 90mt/ 300ft or less; 84% is deeper than 1800mt/ 5900ft.

So, the answer is that we know more about the moon.

What is the recreational dive limit? 40mt/ 130ft

Our depths are limited to our experience and training




​Open Water 18mt/ 60ft Advanced 30mt/ 100ft Deep speciality 40mt/ 130ft

​Tech 40 Tech 45 Tech 50

​Trimix 65 Trimix ----

Maximum regardless of training is 40 mt

We only know a very small part of the ocean

So, we will briefly cover the environment as it concerns us.

What factors must we consider, and how do they affect us?

  • Currents

  • Waves

  • Tides

  • Weather

The ocean has four main basins.

Atlantic, Pacific, Indian and Arctic Ocean

All these are connected. This permits the exchange of seawater as well as plankton and animals.

Four main basins - All connected

Combined with surface currents, it results in a conveyor belt of water around the globe.

Thermohaline Current

These deep-ocean currents are driven by differences in the water's density, controlled by temperature (thermo) and salinity (haline).



The primary cause of water motion is wind energy, namely from the trade winds, Westerlies and (to a lesser extent) the Polar Easterlies.

The energy from these wind systems drives the major Ocean currents. Some of these currents carry 100 times all the Earth's rivers combined.

The Earth's motion also affects major ocean currents.

This helps divers understand the direction of major ocean currents

The term for this is the Coriolis Effect

  • In the northern hemisphere, the currents run clockwise and defect to the right.

  • In the southern hemisphere, the currents run counter-clockwise and defect to the left.

  • Hint. There is an ou in South and an ou in counter.

So, the ocean currents are affected by Wind and the Earth’s rotation.

The major oceanic current off the Pacific coast of the United States of America generally flow in a North to South direction:

Currents = The four principal causes for currents are:

  • Wind blowing over the surface

  • Unequal heating/ cooling of the water

  • Tidal movement

  • Waves


  • Density differences in water masses caused by temperature and salinity variations

  • Coriolis effect

  • Gravity

  • Events such as earthquakes or storms

  • Coastal configuration


Rip Current - Water funnelling back to sea through a narrow opening in a reef or sand bar.

Sometimes, sand from the shore washes away and builds up offshore under the sea surface to form a sandbar. After waves break over the sandbar, much water builds up close to shore. Channels are eventually cut through this bar by the movement or force of the water, breaking the normal flow of seawater on its return to sea after washing ashore. This causes the water to rush out into the deep in narrow paths, giving rise to rip currents. Jetties projecting out to sea can also cause rip currents because they divert the normal flow of current.

If caught in a rip current, establish positive buoyancy and swim parallel to the shore.


A longshore current is an ocean current that moves parallel to the shore. It is caused by large swells sweeping the shoreline at an angle and pushing water down the length of the beach in one direction.


  • Upwelling is when deeper, cool, nutrient-rich water rises to the surface to replace the water driven out to sea by offshore winds. After a few days, visibility may drop due to plankton growth.

  • Downwelling is a vertical current caused by onshore winds that causes surface water to pile up, which then pushes water deeper into the ocean. Downwelling removes nutrients, which may result in a reduced productivity of surface species and an increased productivity of bottom species.

If caught in a downwelling while diving on a wall, put air into your BCD and move quickly away from the wall.



The primary cause is wind.

Waves are defined as a transmission of energy through matter.

Disturbing forces cause waves.

Restoring forces resist them.

Disturbing forces include

  • Wind

The most common disturbing force for waves.

Restoring force for small waves (capillary waves) is surface tension

Restoring force for large waves is gravity

  • Seismic Activity

Include earthquakes and volcanic eruptions

Restoring force is gravity

  • Changes in gravity

These are tides. Tides are waves but have characteristics that distinguish them significantly from what we think, so we talk about them separately.

Restoring force is gravity and the Coriolis effect.

Waves tend to organise themselves into patterns. Waves travel at different speeds. The longest waves will outrun the smaller ones. Eventually, only waves of similar wavelengths are left travelling together.

These are called SWELLS. It is simply a rise and fall of a uniform wave pattern.

SURGE is created by waves passing overhead in shallow water.

Waves break when the depth is about the same size as the waves. (or 1.3X)

Tsunamis are shallow water waves, and while they are called tidal waves, they have no relation to tides. They have very long wavelengths that are nearly imperceptible as they travel. Vessels may rise and fall about 1mt when a tsunami passes, but they do so gradually. It is only when it reaches shore it becomes much higher.

Diving and waves

If you notice that the weather forecast for the next day's dive indicates that it will be windy, you might consider changing the planned site for one that’s more protected if you are concerned about excessive waves.

If you're making a shore dive with a buddy and entering through mild surf, you should have all your equipment in place and carry your fins. When a wave approaches, stand sideways, leaning into it.

If conditions allow, wade into chest-deep water before donning your fins.

If conditions warrant that you don your fins at the water’s edge, you and your buddy can take turns steadying each other.

Once you’ve got your fins on, continue to help each other as you carefully shuffle backwards or perform a sideways “crab walk” into the water.

If you are diving and are lower on gas than you would like but not yet at ascent pressure, it’s best to continue to the exit point underwater if the surface is choppy. You should slow down and set a pace that slows your breathing and ascend to a shallower depth if possible.



Responsible for (usually) twice daily rise and fall of sea surface

Tides can influence

  • Currents

  • Visibility

  • Depth

  • Marine life

  • Distribution of plankton

Diving conditions can be affected sometimes positively and sometimes negatively.

Tides result from a gravitational interaction of the Earth, Sun, and Moon. The cyclical nature makes tides predictable.

Tides are important in determining when specific dive locations will experience strong currents, changing depth and visibility.

The duration and range of the tides depend upon the relative position of the Sun, the Earth and the Moon. The features of a location, such as the shape of bays and estuaries, also can magnify the intensity of tides. Funnel-shaped bays, in particular, can dramatically alter tidal magnitude.

What is the best time to dive?

Slack tide, when high tide peaks, is also called slack high tide.



VISIBILITY = Principal Factors that affect visibility

  • Water Movement (Currents, tides, waves)

  • Suspended particles

  • Weather (for example, excessive rainfall can reduce visibility)

  • Bottom Composition

RAINFALL - In most environments, excessive rain can affect diving conditions by reducing visibility. In addition to having less light because of the heavy rain, rain carries mud and sediment to the water in many areas. This can cause visibility to be reduced just a bit or so much that diving becomes impossible.

THERMOCLINE is a steep temperature gradient in a body of water, such as a lake, marked by a layer above and below which the water is at different temperatures.

HALOCLINE is a Greek word. Halo means salt, and Cline means slope or graduation. It is where fresh water that has fallen as rain meets the salt water from the sea.

Water with a higher concentration of salinity sinks below water that is less saline; therefore, saltier haloclines lie below less salty ones.

To help the environment, dive leaders should:

  • Maintain neutral buoyancy to avoid accidentally touching aquatic plants or animals while diving.

  • Not touch or handle any delicate aquatic organisms, especially creatures with which they are not familiar.

  • Participate in Project AWARE activities such as beach cleanups, etc.




Hint. Port has 4 letters, as does left.

Port (the drink) is red, as is the colour of the light used on the port side.


Green lights are used on the starboard side.

  • If you are facing the stern (back of the boat), these positions don't move; they remain on the same sides of the boat as usual, so port will now be on your right and starboard on your left.





Always put seasick people on the Leeward side.

While exiting the water, it’s a good habit to keep your mask on and regulator in as you climb the boat’s ladder in case you fall back into the water. A regulator can also protect you from any boat fumes.

Would you like to test your knowledge on

The Environment You Dive

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5-point descent (SORTeD) Signal Orientation Regulator Time Elevate, Equalize and Descend

5-point ascent STELaR) Signal Time Elevate Look up Ascend and Rotate


  1. Normal Ascent- The best way to ascend from every dive. With plenty of air and not an emergency

  2. Alternative Air Source - Low on air OR out of air, and buddy is near

  3. Controlled Emergency Swimming Ascent (CESA) - Buddy is further away than the surface, you have NO air, and you are around 9-10mt deep (READ BELOW)

  4. Buoyant Ascent - Emergency only. Out of air, buddy too far away and too deep for a CESA. Drop your weights and get to the surface as quickly as possible. DCI is better than drowning. This skill is not taught, as even practising this is dangerous.

CESA (Controlled Emergency Swimming Ascent)

When you are out of air, your buddy is too far away (or further away than the surface), and you are 9 mt or less.

Divers must:

  • Retain your regulator in your mouth.

  • Not drop your weights. Remember that in an emergency, you ditch weights only when you doubt your ability to reach the surface.

  • Not use the control line for assistance – the line is only for the instructor to use for control and emergency stopping.

  • Maintain a normal ascent rate. (at sea level this is 18mt/ 60ft per min)

  • Make a continuous sound throughout the ascent.

  • Resume normal breathing if you stop the ascent or experience any difficulty.

  • Orally inflate the BCD or drop weights upon reaching the surface.

In brief- With all equipment in place, look up, reach up, prepare to vent excess air from the BCD and swim at a normal pace towards the surface while making a continuous sound. Establish buoyancy at the surface.

You retain your regulator in place during a Controlled Emergency Swimming Ascent (CESA) when you run out of air because the remaining air in your tank expands upon the ascent, which might be just enough for a couple of breaths. Also, if the urge to breathe is too strong, it is better to breathe nothing than breathe water.

Emergency weight drop, either confined water or open water.

With multiple weight systems or pockets, it’s not always necessary to drop all the weight – just enough to become positively buoyant. With a weight belt, divers must pull the belt away from the body before dropping it.

All weight systems must be quick-release

* Regardless of the weight system used, the objective is to quickly release the weights and pull them clear of your body

Alternate Air Source

When you are out of air OR low on air, and your buddy is close by.

(Where) in the triangular area formed by your chin and rib cage.

This helps a distressed diver locate air quickly or for you to share gas immediately. It also assures that all the hoses are maintained in an area that does not drag or snag on the environment.

Disconnect LPI

To simulate the stuck inflator, hold the button down with one hand while disconnecting the hose with the other. Use a grip that doesn’t interfere with disconnecting the low-pressure hose. Either the instructor or the student diver may simulate the stuck inflator.

Emphasise pressing the hose toward the connector to make the release easier and venting the BCD to prevent excess positive buoyancy.

Free Flowing Regulator

If a regulator "breaks", the regulator will give you ALL the air available and not close off the air. This means the air will come out fast.

You can breathe around that fast-flowing air and make a controlled, safe ascent. You sip the air, using your tongue as a water dam. The air will come out fast enough to prevent water entering, if any. Remember not to seal the regulator in your mouth; that will force air into your airway. Sip the air and surface from the dive.

The air will be very cold as it is pressurised air being released from a dive tank. Use your lips as a tooth guard if this feels uncomfortable on sensitive teeth.

If you want to know why the air is chilled when released from a high-pressure environment, read about it in Charles Law.

Skin Diving

Hyperventilation (rapid, deep breathing) is no longer preferred as a breath-hold technique in skin diving because it can result in loss of consciousness. Although some use this technique by limiting hyperventilation to two or three breaths, it is better to breathe from your diaphragm, or “stomach breathe”, in preparation for a skin dive.

If you would like to understand more about skin diving and freediving, check out our blog on Physiology


Being able to communicate under the water is important when you can't use words. How do you tell someone what you have seen, what that cool fish was, what you want, how much air you have? How do you communicate a problem or the solution to that problem? What if there is an emergency? There are many standard signals that all divers must know and there are some that vary between regions. Discussing signals before a dive ensures that everyone is clear and up to date on the underwater communications that will be required on that particular dive.

Some very important ones have been listed below.


  • A clenched fist brought to the chest means a diver is low on air

  • A slashing motion across the throat is out of air.





Above 300mt to 3000mt

  • The PADI RDP, other tables and dive computer models assume surfacing at sea level, and so diving at altitudes above 300mt/ 1000ft requires special dive decompression procedures because there’s less atmospheric pressure at the surface, which affects dive table and dive computer calculations, i.e., the ambient atmospheric pressure at altitude is less than at sea level.

  • Partial pressure decreases, and the percentage remains the same.

  • At altitudes higher than 300mt/ 1000ft, the reduced atmospheric pressure when surfacing could make the tissue pressure gradient (the difference between the pressure of the nitrogen dissolved in the tissues and the surrounding/ambient pressure) too high, raising the risk of DCS. The recommended ascent rate, therefore, is 9 metres/30 feet per minute or slower.

  • According to dive decompression theory, actual depths must be converted to theoretical depths to find No Decompression Limits (NDL) on the RDP. To use theoretical depth tables, you must know the altitude of the dive, and the special procedures include converting the actual depths to theoretical depths.

  • A slower ascent rate of 9m per minute is used when diving at altitude.

  • Hypoxia and hypothermia are issues at altitude

  • Recommended no more than two dives a day

  • Make a higher altitude dive first, followed by a lower

  • With the RDP, your first option is to wait six hours after arriving at altitude before making your first dive. Much like after a dive when diving at sea level, for planning purposes, this clears residual nitrogen.

  • Concerns for flying apply after diving and driving to higher altitude

  • Safety stop between 4mt – 3mt

Remember from our blog on equipment.

Altitude, Boyle, Capillary (ABC):

Capillary gauges are best suited for altitude dives and are based on Boyle's Law.

Gas Narcosis at Altitude:

As we know from Physiology, gas narcosis generally occurs as the partial pressure increases (Dalton's Law). This forces the inert gas, nitrogen (although other gases can also cause narcosis), to dissolve in the lipid membrane of the neurons.

The effect may, however, vary depending on other physiological factors. Anything that could have an impact on the circulatory system may affect the physiological effects. These can include Carbon Dioxide buildup, hydration levels, temperature, etc.

Even though partial pressures are lower at alititude, conditions such as cold water from a mountain lake, dehydration from dry air at altitude, and overexertion, may predispose a diver to gas narcosis due to changes in blood flow to the cerebral cortex.

So, gas narcosis may happen at shallower depths regardless of the lower partial pressures at altitude. However, this seems more because of extenuating environmental circumstances than the actual altitude.



Check your air more frequently. Twice as much as on shallow dives

Safety stops are required.


​SIGNS (something you see)

SYMPTOMS (something you feel)

Inappropriate behaviour Short attention span Slowed thinking Impaired vigilance Disregard for safety Stupor or semi-conscientiousness Failure to follow the dive plan

​Rigid, inflexible thinking Difficulty concentration Loss of good judgement Short-term memory loss Lack of concern for a task or personal safety Unjustified elation Drowsiness or feeling intoxicated Anxiety

Narcosis may be alleviated by bringing the diver to shallower depths, with no after-effects.

If you would like to know more about why this happens, check out our blog on Dalton's Law

​Emergency decompression

​If you exceed a no-stop limit by no more than 5 minutes, make an 8-minute stop at 5mt. Do not dive for 6 hours

​If you exceed a no-stop limit by more than 5 minutes, make a stop at 5mt for at least 15 min (gas supply allowing) and do not dive for 24 hours

​If you accidentally miss an emergency decompression stop, stay calm. Do not re-enter the water. Breathe 100% oxygen and monitor for any DCS symptoms. Do not dive for 24 hours

Decompression Sickness

​SIGNS (something you see)

​SYMPTOMS (something you feel)

​Favouring and arm or leg Paralysis Unconsciousness Staggering Collapse Coughing spasms Blotchy skin rash

​Pain, often in limbs and joints Numbness, tingling or paralysis Fatigue and weakness Skin itch Shortness of breath Dizziness and vertigo

Factors contributing to DCS

  • Dehydration

  • Fat or poor fitness

  • Age

  • Exertion before, during or after a dive

  • Injuries or illness

  • Alcohol use

  • Cold water

  • Hot showers before or immediately after

  • Carbon dioxide increase

  • Exposure to altitude

Read our blog on physiology for more information

Special equipment

  • Adequate exposure suit

  • Weights – enough for a safety stop

  • Reference line

  • Cylinders – high capacity/ side mount

  • Alternative air source – pony bottle

  • Torch – It gets dark below, and you also lose a lot of colour at depth



Participating in a Discover Local Diving experience is recommended

  • When the divers are in an area/environment where they have no previous experience.

  • Are a certified diver (regardless of level of certification)

A local environmental orientation includes…

  • Entry and exit techniques (i.e., boat or surf)

  • Marine life

  • Hazards and points of interest

  • Orientation

  • Currents

  • Anything distinct to the dive site. Each dive site might be different and warrant its own orientation (DLD)



Hypothermia concerns. If you start shivering uncontrollably, end the dive, exit the water, and seek warmth.

Distribute weights evenly over the body. You can use

  • Accessory weights like ankle weights

  • On a belt, using smaller weights that you can spread out

  • Integrated weights

  • Divide between 2 systems like integrated BCD and weight belt

First, do an orientation in confined water or a controlled environment.

If you are diving in a dry suit in low visibility where it’s difficult to orient yourself, and you feel yourself starting to rise, and then your leg catches on some fishing net that tangles around a fin, the best course of action would be to release some air from your BCD and/or dry suit before doing anything else and try to free yourself.

Argon is a heavy gas that insulates better than air does. Although there is some debate about its effectiveness as a dry suit inflation gas, many divers (especially tec divers) use it when diving dry. Argon systems consist of a small, specially marked cylinder that’s typically mounted valve-down on the left side of your cylinder(s) or BCD/harness. The regulator has no mouthpiece (so no one accidentally breathes from it), as well as an overpressure valve.

If a dry suit seal that has recently been replaced or, on a new suit, feels too tight, you can trim it with scissors in small amounts until you get the correct fit. Latex seals are tapered and have a series of trim lines (small, raised lines on the outside of the seal) that start at the seal opening and progressively get bigger. When trimming, use these to keep the lines even and use good scissors.



Each diver must personally analyse their tank

Oxygen Toxicity

​Pulmonary toxicity

​CNS toxicity

​• Caused by continuous exposure to elevated oxygen partial pressure greater than .05 bar. • Symptoms and signs include burning in the chest and irritated cough. Usually, it resolves itself by ceasing diving for several days. Not considered immediately life-threatening or hazardous.

​• Caused by exposure to oxygen partial pressures greater than 1.4 BAR • Symptoms and signs include Visual disturbances, Ear ringing, Nausea, Twitching muscles, Irritability and Dizziness. VENTID The most serious is convulsion (hyperoxic seizure) which can cause a diver to drown. These powerful convulsions may cause unconsciousness, and the diver may lose the regulator mouthpiece.



  • Reduce anxiety and confusion.

  • Avoid long surface swims.

  • Increase dive plan effectiveness.

  • Avoid buddy separation and conserve gas.


Used in every course

Your compass directs you one way, but you feel like you are going the wrong way; what should you trust? Trust your compass; it's more reliable than your instincts underwater.


Turn Angle

Number of turns needed to complete pattern




​1 turn




​2 turns




​3 turns

When navigating a square pattern underwater, if you begin your course on a 50-degree heading, how many turns will you require, and what will your new heading be?

Three turns: 140, 230, 320

An easier way is:

Once your heading is set with north between the index marks, do not touch the bezel; instead, move your body, follow the lubber line and use the cardinal points (North, South, East, and West). 90º of north is either East or West, depending on which way you turn. So rather than adjust the bezel and maybe use bad mathematics underwater, use the cardinal point method.

Starting point - North (between the index marks. The actually heading is irrelevant)

Start North between index marks

1st turn -East (or West)

2nd turn - South

3rd turn - West (or East)

Bring you back to your starting point

I recommend using this method, especially on night dives.

​Natural navigation

​Before entering a dive, take note of

While underwater

​-Wind, current, tide. -Angle of sun. -Offshore objects. -Depth finder.

​-Light and shadows. -Water movement. -Bottom composition and formations (sand ripples parallel to the shore.) -Bottom contour. -Plants and animals. ­-Noise.

The best way to measure distance.

Arms span These are always the same distance. The others (kick cycles, timed swim, air consumption) rely on what equipment you are using, the current strength, the velocity of the swim, etc.

You’re diving close to shore but in very low visibility, and you’re no longer sure where you are or which way is back to shore. Sand ripples (generally parallel to the shore) and depth change could immediately help you.

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Each student must have their own underwater light. A backup underwater light and a chemical/ marker light are recommended.

Choose a night diving site you are familiar with.

Use equipment you are familiar with


  • Visibility

  • Surge/current

  • Surf and waves

  • Water temperature

  • Tides


  • Mod – high surf

  • Mod – strong current

  • Poor visibility

  • Kelp, nets, lines etc

  • Heavy surge

  • Overhead environments


Back and forth – help or emergency

Large circles – OK

Slowly waving up and down – attention

If you accidentally hit the reef and drop your torch, ensure you have not hurt yourself first. Examine your injury with your backup light before attempting to retrieve your torch.



Buoyancy is the best skill we can master. Most importantly, we are protecting the aquatic environment, but we also save air and are more comfortable in the water.

Good buoyancy is also important for completing safety stops. In technical diving, good buoyancy is essential for decompression stops that can last a long time.

Taking the perfect photo means being perfectly neutrally buoyant in the water.

Buoyancy check

  • Enter water too deep to stand with all equipment.

  • Breathe from the regulator and deflate the BCD completely.

  • Holding a normal breath, floating in a vertical position, you should float at eye level.

  • Add or subtract weight until floating at eye level.

  • Final check: you should sink slowly when you exhale.

If done with full cylinders, add weight to compensate for air used during the dive – typically about 2 kg/5 lb.

When should we do a buoyancy check?

  • New environment

  • New equipment

  • Long time without diving

We should adjust our buoyancy due to:

  • Suit compression

  • Gas consumption

  • Depth change

You’re planning a dive in the ocean wearing an equipment configuration you’ve only worn in fresh water. You should perform a buoyancy check to account for the change to salt water.

An object will be more buoyant in salt water than in freshwater. If you would like to know why, check out our blog on Archimedes Principle

Proper weight gives you more control in the water. You should not use more than you need.

  • If you have too much weight, you will be overweighted, dragging your lower body down. More air must be added to the BCD to compensate, and you will move less efficiently through the water.

  • Underweighted, you will be swimming in a downward position as you constantly try to compensate physically.

To change the buoyancy of an object that is neutral, you can

  • Add or subtract weight

  • Increase or decrease volume or displacement



Participating in a PADI ReActivate program is recommended when a diver wants to refresh their skills after a period of inactivity.

It can also be used to

  • Upgrade Junior Open Water divers - For upgrading to an adult OW certification card.

  • Upgrade Scuba Diver -as a refresher before the skills

  • Continuing Education Assessment - Assessment of divers readiness to continue

  • Certified Divers from Other Organisations - to refresh the skills of divers from other organisations.



•Rule of thumb is to use a lift bag for objects heavier than 4-7kg/10 pounds but not more than 45kg / 100 pounds.

• When you locate an object that you are going to recover by lift bag, the first step is to mark it by attaching a buoy or line. You do this so that if the object slips or sinks during recovery, you do not have to search again

• Rig the lift bag to the object

• When possible, use nylon pre-stretched for rigging. Nylon holds up well in the water, and the knots hold well in it, even when wet

• Use the appropriate knot. This means one that will hold but one that you can untie later. (See knots)

• Choose a lift bag with the lifting capacity as close to the object’s negative buoyancy as possible. When the bag is full, the expanding air will bubble out the bottom. If you use a bag significantly larger, you run the risk of a runaway ascent unless you vent the expanding air

• Put a puff of air in, just enough to make it stand up and pull tightly on the rigging

• Using your alternate, slowly inflate in short bursts. Do not use primary because it is unnecessary task loading. Hold the inflator so you can pull it free easily and so it cannot tangle in the rigging. After each burst, pull up to see if you can lift the object. Continue until the object rises gently when you pull up and hover off the bottom. You are trying to make it NEUTRALLY buoyant, not positively buoyant

• Do NOT lean over the object, as you will be in its path if it takes off suddenly. Important if stuck in mud bottoms as the suction may be holding it down (rock object to help break suction)

• Once hovering, reinspect rigging. When ready to ascend, tow object horizontally along the bottom to ensure a clear area for ascending and avoid a tiring surface tow

• Position yourself at the side of the object and level with the lift bag

• Do not add air while ascending. Expanding air will increase buoyancy, and the bag and object will begin rising

• Either ascend with the object or let it ascend by itself. If the bag capacity is close to the object's negative weight, expanding air will bubble out the bottom, making runaway ascent unlikely. If larger capacity, then if a run-away ascent occurs, it will accelerate as expanding air increases buoyancy, and when the bag pops the surface, it will spill and sink

• You may choose to ascend with the bag, controlling its accent rate by venting expanding air.

• Ascend at a maximum of 18mt / 60ft per minute

• You need to vent air from both your BCD AND the lift bag

• If you have trouble controlling the ascent, let it go. Be sure to keep your hands and gear clear of the rigging always to avoid getting snagged and dragged up. If you must let a runaway bag go, swim horizontally away as quickly as possible to avoid being directly underneath in case it re-sinks.

• After you reach the surface, add air to give plenty of positive buoyancy. You may tie it to your float


Different patterns depend upon

  • Bottom topography and equipment availability

  • Size and weight of the object and size of the search area

  • Water conditions and visibility.

Expanding Square

Good for a single search team

Know where the diver/object (medium-sized) was last seen

Good to moderate visibility

Recall system

Effective over a wide area

Rough terrain and flat bottom

Quick to set up, easy to plan

U-shape pattern

Good for more than 1 team

In good visibility

Good for small to large objects.

Good over a variety of topography. Best over a flat bottom but can be effective over an uneven bottom or even in a current if done with care.

Circular pattern

Need use of rope or line

Good in poor visibility

Need center point

Good on a flat bottom for small objects in a small area

Jackstay pattern

Covers a large area with poor visibility. This can be done carefully in a current.

Needs a flat bottom.

Underwater line communication

1 pull Attention or stop

2 pulls, OK? Ok

3 pulls I`ve finished the leg (or circle or length of pattern)

4 pulls come to me, or let’s unite

continuous pulls emergency



Generally recommended knot for making a reliable, easy-to-untie loop in a rope

Join two objects together. Easy to untie.

Double half hitch

Tie a knot around an object.

Sheet bend

Join two ropes of different sizes.



You decide to release your delayed surface marker buoy (DSMB) to show your position. You have the DSMB line attached to your reel. You should inflate the SMB or DSMB yourself, keep hold of the reel, release the line, and keep tension on it. Do not attach it to your equipment or yourself.

SMBs and DSMBs do exactly the same thing and are intended for the same purpose, to let people at the surface know where divers are located.



​Surface Marker Buoy

​Delayed Surface Marker Buoy

  • ​A long bright collared tube deployed at the surface after a dive

  • Can be attached to a line and towed during the entire dive

  • DSMB is only deployed at the end of the dive, on the ascent or during the safety stop.

  • The DSMB is deployed to alert the surface that divers have started to ascend.

  • Generally deployed at the safety stop, so have lines that measure 5mt and up. Always tied to a line

  • DSMB has an over-inflation valve and no spill design



Salvage rights determine who owns something lost at sea. Different areas have different laws.

Antiquity protection is to protect wrecks so that archaeologists can study them. Also, in some areas, wrecks are war graves and should not be disturbed. If you find something near a wreck, you should note the location, take a photo if you can and report it to authorities or the local museum.

Apart from removing items as part of an authorized project or items that have been recently lost or debris (litter), removing objects from underwater should be avoided as it can destroy historical information and/or make the site less interesting for others.


  • Sharp objects

  • Entanglement

  • Aquatic life

  • Unstable structure

  • Surge pockets and suction

Overhead environments

Special training, special equipment, special procedures……

  • Loss of direction

  • No direct surface access

  • Restricted passages

  • Falling objects

  • Silt

Assessing and navigating a wreck, take note of:

  • Possible hazards

  • Points of interest

  • General condition

Navigating wreck

  • Follow wrecks layout

  • Feature reference

  • Base line

Compasses may be inaccurate some or all the time if you are too close to the wreck, as steel and iron attract the compass needle.

This can occur with both analog and digital compasses.

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min age - NONE

Rescue breaths

1 person 2:30

Compressions per min 100

Arterial Bleeding – Bright red blood that spurts from a wound in rhythm with the heartbeat. Death can occur in 1 minute.

Venous Bleeding – Dark red blood that steadily flows from a wound. Also, life-threatening and must be controlled

Capillary Bleeding -Slow bleeding and is controllable

The best method of managing bleeding is to apply a dressing and direct pressure.

If blood soaks through the dressing, you should maintain direct pressure and apply additional dressings over the first.


LOOK – Place your ear close to the patient’s mouth, turn your face to their chest with your ear next to their mouth and look to see if the chest is rising and falling.

LISTEN – Listen, with the ear that is close to the mouth, for signs of breathing

FEEL – Feel for breath on the ear. You can also place your hand on the patient’s chest.

ALSO USED NOW FOR A CIRCULATION CHECK instead of looking for a pulse



Decompression Sickness (DCS)

Inert gas forms bubbles in tissues and the bloodstream as it comes out of solution due to high supersaturation following ascent

DCS can appear 15 minutes to 12 hours but can occur up to 36 hours after a dive

Type 1 - Pain only, limb and joint pain, cutaneous

Type 2 – Neurological, numbness and tingling, paralysis, weakness, and unconsciousness

Lung over expansion.

Pneumothorax, Subcutaneous emphysema, mediastinal emphysema, Arterial Gas Embolism (AGE)

* AGE = most dangerous - Air bubbles enter the bloodstream through a lung rupture, usually following a breath hold ascent.

Lung over-expansion injuries have immediate signs and symptoms that appear upon surfacing.

Decompression Illness

The field term for both as first aid is the same for both decompression sickness and lung over-expansion injuries.

Upon surfacing, Decompression Sickness can appear 15 minutes to 12 hours but can occur up to 36 hours after a dive

Lung Overexpansion occurs immediately and up to within a few minutes.

1ST Aid is the same for both DCS and Lung Overexpansion Injury, hence a blanket term of DECOMPRESSION ILLNESS is used for both.

1. Treat all DCI as serious, even pain-only DCS.

2. Give the patient oxygen (preferably 100 per cent) as soon as possible.

a. Lowers alveolar nitrogen to accelerate elimination from tissues

b. Raises blood oxygen levels to assist tissues with blood flow reduced by bubble blockage.

3. Keep a breathing patient lying level on the left side, head supported (recovery position).

a. Helps keep the airway clear if the patient vomits.

b. Lying level helps ensure blood flow to the brain.

c. Advise patient not to sit up or walk around, even during transport or if feeling better.

4. Lay the non-breathing patient on their back for rescue breathing/CPR.

5. Contact emergency medical care.

Types of oxygen systems.

  • positive pressure (beyond the scope of this training),

  • continuous flow (used with rebreather mask and pocket mask)

  • non-resuscitator demand valve

Never re-enter the water for recompression.

Recompression takes hours and may need drugs and fluids. You also won’t be able to keep the diver warm long enough in the water.

Signs a diver may have a problem at the surface

  • Giving distress signal

  • Struggling on or just below the surface

  • High treading or finning

  • Rejecting equipment

  • Clinging or clambering

  • Not moving



​Asks for help Responds to directions or questions Can assist in efforts to help Recovers quickly

​Overwhelmed by stress or fear Abandoned rational response Reacts through instinct and fear Rejects gear (mask on forehead, spitting out regulator or snorkel) Eyes wide Perceptual narrowing Does not respond to directions or questions Passive panic Fails to establish buoyancy

In a panicked diver, perceptual narrowing is a decrease in broad awareness through a close focus on a perceived threat.

Your first concern should be getting that panicked diver buoyant.

Types of Diver Stress



​Cold Seasick Narcosis Fatigue Illness or injury Alcohol Drugs

​​Peer pressure Task loading Individual beliefs Perceptions

Psychological stress is stress due to the diver’s reaction to perceived “threats” in the environment, including perceived causes of actual bodily harm and “threats” to self-esteem. The diver’s beliefs and attitudes play a major role in psychological stress, so the stressor may be imagined or real.

Psychological stress often results from physical stress. For example, fatigue or being tired can trigger psychological stress if the diver fears being unable to make it safely to the boat or shore. An overexerting diver can feel air starved and fear that the regulator can’t deliver enough air.

What is the most common cause of diving accidents??? Poor judgement.

​Diver Inwater Rescue

​​Less than 5 minutes from help, tow the diver while continuing to provide rescue breaths

More than 5 minutes from help give rescue breaths for one to two minutes while watching for signs of movement or response. If no response, then cardiac arrest is likely. Rescue breaths do not benefit someone without chest compressions. CPR is impossible in the water. Discontinue rescue breaths in favour of speed and tow the victim as quickly as possible to safety, where CPR and rescue breathing may commence.

Primary consideration for an unconscious diver at the surface? Getting that diver to a place where first aid, ventilations and/or CPR may be effectively administered.

Your priorities at the surface are:

  • Always establish buoyancy first for both you and the victim

  • Check for breathing. if they are not breathing, you assume no pulse. Do not waste time looking for a pulse.

  • Providing regular rescue breaths.

*Respiratory arrest can often be corrected with rescue breaths

*If rescue breaths are not immediate, cardiac arrest will occur

*The survival rate of respiratory arrest is much higher than cardiac arrest

In most instances, brain damage occurs in as little as 4 – 6 minutes without oxygen. However, for reasons not understood (especially in cold water), immersion can make revival possible even after long periods.

Evacuation of a dive accident victim

Arrange for the fastest mode of transportation to the nearest emergency medical facility. This should be in the Emergency Action Plan of each dive site and readily available in an emergency.

Drowning in very cold water can make revival possible, even after fairly long periods of time.

Regardless of how long a person has been submerged, in cases of drowning, the primary first aid for a nonbreathing diver after reaching the surface is immediate rescue breathing.

A revived near-drowning patient who appears fully recovered must be medically evaluated……while drowning symptoms usually occur immediately, they can start and/or worsen eight or more hours after the incident.

If a diver loses consciousness during a dive but is fine after, they are still at risk. They may appear fully recovered, only to suffer hypoxemia hours after the incident. This is called secondary drowning. Without therapy, this is often fatal.

Giving a near-drowning victim oxygen is the top priority.

You can read more about this in Physiology.

Preferred method of rescue breaths…

Mouth to Pocket mask (protects airways, protects against disease, can attach O2)

Buddy breathing

is sharing a single regulator. Each diver takes two breaths from the regulator before passing it to the other.

Not used as often now as all regulators have an alternate to share with a diver low on air or out of air, and this is the first option in an out-of-air emergency.

Thermal Injuries



​Faint or dizziness Excessive sweating Cool, pale, clammy skin Nausea, vomiting Rapid, weak pulse Muscle cramps

​Throbbing headache No sweating Red, hot, dry skin Nausea, vomiting Rapid, strong pulse May lose consciousness



Uncontrollable shivering Impaired coordination Impaired mental process Vasoconstriction

​Vasoconstriction stops Shivering stops Drowsiness Uncoordinated Loss of conscience

Marine life injury

  • Local swelling

  • Numbness or paralysis

  • Excruciating pain

  • Nausea

  • Respiratory/ cardiac arrest

Three types of aquatic life injury

  • Bites

  • Cuts, abrasions, and punctures

  • Venomous stings

For Jellyfish stings

Remove tentacles with forceps. Never remove with fingers

Clean with salt water, acetic acid, vinegar or ammonia solution. Never use fresh water.

If you exit the water after diving in warm tropical seawater and notice your buddy has a red, raised welt on their arm, it is most likely caused by a jellyfish, and you should rinse the wound area with vinegar.

Gas Narcosis

It's not directly hazardous. Hazards come from impaired judgement and coordination, a false sense of security, euphoria and a lack of concern for safety that may lead to bad decisions. Divers may also feel anxious or uncomfortable.

Carbon monoxide poisoning

Cherry red lips, nail beds, nausea,




B – BCD/Buoyancy-

Check everything is connected and functioning. Test the inflate button and all the deflate valves. Knowing how your buddy's gear works in an emergency is essential.

W – Weight

Ensure that each diver has their weight and that they are secure. Tug gently at integrated weight pouches to confirm that they are locked in. Check weight belts are right-hand release and weights are uniformly distributed. Check rear BCD weight pockets and other places where weights may need adjusting.

R – Releases-

Check each release is secure and you are familiar with the design. In an emergency, you need to know how to assist your buddy. Each BCD is different, but you will generally find releases on the shoulders, chest and belly. Do not adjust unless loose. Check that the tank strap is in place to catch the tank if it slips while entering the boat or while walking. Check that the tank band is not too high or low. Check hoses and other items are positioned correctly and not twisted or trapped.

A – Air-

FIRST, check that the air is opened all the way. Do this first so that you do not accidentally turn the air off without a further safety step. THEN breathe from the regulator while looking at the SPG or dive computer that is air-integrated. This will ensure the tank is open and full, the gauge works, and the air tastes good. Having both divers breathing simultaneously from a single tank can be helpful. One from the primary and one from the alternate, to see that the regulator can support two divers, then swap and check for the buddy. Ensure AAS is placed in the triangle between the chin and the bottom of the ribs.

F – Final Check-

Finally, check that you have everything required for the type of dive that you are doing. (mask, fins, dive light, camera, SMBs or DSMBs, whistle, etc.)

Do a final check of hoses and other objects.

Do a quick head-to-toe to check everything is good to go.

Remember by

Begin With Review And Friend

Blond Women Really Are Fun

Beer With Rum And Fries

and there are many, many more politically incorrect versions

NOTE: The most common reason for cylinders slipping in nylon tank bands is adjusting the band while it is dry.

Make sure you check your tank while setting up your equipment and your buddies during your buddy check



What is a Safety Stop?

A safety stop is added for safety at the end of a non-decompression recreational dive. The standard dive procedure for a safety stop is to do one on any dive below 10 mt/32 ft at a depth of 5 mt/15 ft for 3 minutes. This allows the diver's body to decompress after time spent at depth.

The appropriate time to make a safety stop is

  • At the end of a particularly long or deep dive

  • When you near the no decompression limits of your table or dive computer

  • At the end of virtually every dive, provided there are no other safety concerns such as extremely low air supply

What is a Deep Stop?

A deep stop is a second stop that is done at 50% of the maximum depth of your dive for 30 to 60 seconds. This is not a substitute for a safety stop at 5 mt but an additional one for added safety after a deep dive.

What is a Decompression Stop

A decompression stop is mandatory on all dives that have exceeded the no-stop decompression limit.

Dive Smart.

  • Never dive to the limits of air, depth or time.

  • Dive Safely

  • Ascend slowly. No more than 18mt per minute

Be S.A.F.E. -Safely Ascend From Every Dive

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The Environment You Dive

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Nevin. (2022). A Guide to Decompression Stops – II. (2022, October 18). SMB or DSMB: What is a safety sausage really? - DIVEIN.

Divemaster Course Instructor Guide (1999 edition). (2005). PADI.

The Encyclopedia of Recreational Diving (3rd ed.). (2008). PADI.

Padi rescue diver manual. (2004). International PADI.

PADI Search and Recovery. (2004).

PADI Night Diver (2004)

PADI Wreck Diver (2003)

PADI Deep Diver (2003)