- Tracy Gunn
Dive Skills and the Environment IDC Dive Theory
Updated: Jul 5
Dive Skills and the Environment can feel overwhelming as it seems to cover so many different topics but really, 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 understand that vast and diverse world of diving and to give you a head start for your IE.
DIVE SKILLS AND THE ENVIRONMENT
THIS IS ONLY THE TIP OF THE ICEBERG AND IS DESIGNED ONLY TO REFRESH KNOWLEDGE AND NOT TO REPLACE INDEPENDENT STUDY
THE ENVIRONMENT YOU DIVE IN
What do we know more about?
The moon or the ocean???
Oceans cover 71% of the Earth’s surface with an average of 3800mt/12450ft
3% of this is fresh water with ¾ of that frozen in Polar ice caps. Another 20% is ground water
Given that 84% of the seafloor rests at more than 1800 mt/ 5900 ft, most of our knowledge is confined to depths of 90mt/ 300ft and less.
So the answer is, we actually know more about the moon.
What is the recreational dive limit? 40mt/ 130ft
Our depths are limited to our experience and training
RECREATIONAL | TECHNICAL | TRIMIX |
Open Water 18mt/ 60ft Advanced 30mt/ 100ft Deep speciality 40mt/ 130ft | Tech 40 Tech 45 Tech 50 | Trimix 65 Trimix ---- |
We only know a very small part of the ocean
So, we are going to briefly cover the environment as concerns us.
What factors do you think we have to take into consideration and how do they affect us?
Currents
Waves
Tides
Weather
The ocean has 4 main basins.
Atlantic, Pacific, Indian and Arctic Ocean
All these are connected. This permits exchange of seawater as well as plankton and animals
4 main basins - all connected
When 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, which is controlled by temperature (thermo) and salinity (haline)
CURRENTS
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 earths rivers combined.
The Earths motion also affects major ocean currents.
This helps divers understand the direction of major ocean currents
The term for this is the Coriolis Effect
Northern hemisphere the currents tend to run in a clockwise direction and defect to the right
Southern hemisphere the currents run in an counter-clockwise direction and defect to the left
Hint. There is a 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
Also
density differences in water masses caused by temperature and salinity variations
coralis effect
gravity
events such as earthquakes or storms
Coastal configuration
RIP CURRENTS
Rip Current - Water funnelling back to sea through 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, a large amount of 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 shore
LONGSHORE CURRENTS
A longshore current is an ocean current that moves parallel to the shore. It is caused by large swells sweeping into the shoreline at an angle and pushing water down the length of the beach in one direction.
UPWELLINGS AND DOWNWELLINGS
Upwelling is a process in which deeper, cool, nutrient rich water rises to the surface to take the place of the water driven offshore. After a few days, visibility may drop due to plankton growth.
Downwelling is a vertical current that 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.
WAVES
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.
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 basically 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 Coriolis effect
Waves tend to organise themselves into patterns. Waves travel at different speeds. The longest waves will outrun the smaller. 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
Tsunamis are shallow water waves and while they are called tidal waves, they have no relation to tides. They have very long wave lengths that are nearly imperceptible as they travel. Vessels may rise and fall about 1mt when a tsunami passes but they do so very 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 days dive indicates that it will be windy, you might consider changing the planned site for one that’s more protected if you have reason to be concerned about excessive waves.
If you're making a shore dive with a buddy and are entering through mild surf, you should have all your equipment in place and be carrying 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 find that you 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. So you should slow down and set a pace that slows your breathing and if possible ascending to a shallower depth.
TIDES
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 play an important role in determining when certain dive locations will experience strong currents, changing depth and changing visibility
The duration and range of the tides depends 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.
Best time to dive?
Slack tide when high tide peaks also called slack high tide
OTHER ENVIRONMENTAL FACTORS
VISIBILITY = Principal Factors that affect visibility
Water Movement (Currents, tides, waves)
Suspended particles
Weather (example: excessive rainfall can reduce the visibility)
Bottom Composition
RAINFALL - In most environments, you can expect excessive rainfall to affect diving conditions by reducing visibility. In addition to having less light because of the heavy rain, in many areas, rain carries mud and sediment to the water. 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 the higher fresh water, that has fallen as rain, meets the lower salt water, that comes in from the sea.
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.
AREAS OF A BOAT
PORT IS THE LEFT SIDE OF THE BOAT WHEN FACING FORWARD
Hint. Port has 4 letters as does left
Port (the drink) is red as is the light used on the port side
STARBOARD IS THE RIGHT SIDE OF THE BOAT WHEN FACING FORWARD
Green lights are used on the starboard side
If you are facing the stern (back of the boat) these positions dont move, remain on the same sides of the boat as normal, so port will now be on your right and starboard on your left
THE TOILET IS THE HEAD
THE GALLEY IS THE KITCHEN
WINDWARD IS TOWARD THE WIND
LEEWARD IS AWAY FROM THE WIND 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.
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Dive Skills and the Environment
The Environment You Dive
COURSES
OPEN WATER
5-point descent (SORTeD) Signal Orientation Regulator Time Elevate, Equalize and Descend | 5-point ascent STELaR) Signal Time Elevate Look up Ascend and Rotate |
ASCENTS
Normal Ascent- Best way to ascend from every dive. With plenty of air and not an emergency
Alternative Air Source - Low on air OR out of air and buddy is near
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)
Buoyant Ascent - Emergency only. Out of air, buddy too far away and too deep for a CESA. Drop your weights and just get to the surface as quickly as possible. DCI is better than drowning. This skill is not taught as even practicing 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
Retain your regulator in your mouths.
Not drop your weights. Remember that in an actual emergency, you ditch weights only when any doubt exists about 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 if you 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 have run out of air because you may be able to get a few breaths of air as you ascend. The remaining air in your tank expands upon ascent and that might be just enough for a couple of breaths. Also, if the urge to breathe is too strong, it is better to have nothing to breathe than breathing water.
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 quick release the weights and pull them clear of your body
Alternate Air Source
When you are out of air OR low on air and you buddy is close by
(where) in the triangular area formed by your chin and rib cage.
This helps a diver in distress 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 inflator 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.
Emphasize 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 not permit a lot of water to enter, if any. Remember, of course, to not 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. If this feels uncomfortable on sensitive teeth, use your lips as a tooth guard.
If you want to know why the air is chilled when it is 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 understand more about skin diving and freediving check out our blog on Physiology
ADVENTURE/SPECIALITY COURSES
Altitude
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 require 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, 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 2 dives a day
· Make higher altitude dive first followed by lower
· Concerns for flying apply after diving and driving to higher altitude
· Safety stop between 4mt – 3mt
Remeber from our blog on equipment.
Altitude, Boyle, Capillary (ABC) Capillary gauges are best suited for altitude dives and are based on Boyles Law
Gas Narcosis at Altitude:
As we know from Physiology, gas narcosis generally occurs as the partial pressure increases (Daltons 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.
At altitude, even though partial pressures are lower, 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 the flow of blood to the cerebral cortex.
So gas narcosis, regardless of the lower partial pressures at altitude, may in fact happen at shallower depths, although this seems to be more because of extenuating environmental circumstances than the actual altitude.
DEEP DIVE
Check you air more frequently. Twice as much as on shallow dives
Safety stops are required
Narcosis…. | |
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 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 simply 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 Daltons 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 accidently 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 paralysi 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 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
DISCOVER LOCAL DIVING (NOT A COURSE)
Participating in a Discover Local Diving experience is recommended
When the divers are in an area/environment in which 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 that is distinct to the dive site. Each dive site might be different and warrant its own orientation (DLD)
DRY SUIT
Hypothermia concerns. If you start shivering uncontrollably, end the dive, exit the water, and seek warmth
Distribute weights evenly over body. You can use
Accessory weights like ankle weights
On a belt, using smaller weights that you can spread out
Divide between 2 systems like integrated BCD and weight belt
First do an orientation in confined water or in 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 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 a pair of good scissors
ENRICHED AIR
Each diver must personally analyse their own 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 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 Most serious is convulsion (hyperoxic seizure) and can cause diver to drown. These powerful convulsions may cause unconsciousness and the diver may lose the regulator mouthpiece. |
NAVIGATION
Reduce anxiety and confusion
Avoid long surface swims
Increase dive plan effectiveness
Avoid buddy separation and conserve gas
COMPASS
Used in every course
Your compass is directing you one way, but you feel like you are going the wrong way, what should you trust? Trust your compass, its more reliable than your instincts underwater.
Reciprocal | 180º | 360÷2=180 | 1 turn |
Triangle | 120º | 360÷3=120 | 2 turns |
Square | 90º | 360÷4=90 | 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 headings 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, rather 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 ajust the bezel and maybe use bad mathematics underwater, just 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 shore) -bottom contour -plants and animals -noise |
Best way to measure distance
Arms spans These are always the same distance. The others (kick cycles, timed swim, air consumption) rely on what equipment you are using, current, velocity of 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 run parallel to the shore) and depth change could immediately help you.
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Dive Skills and the Environment
Courses Part 1
NIGHT DIVE
Each student must have their own underwater light. A backup underwater light and a chemical/ marker light is recommended
Choose a night diving site you are familiar with.
Use equipment you are familiar with
Considerations
Visibility
Surge/current
Surf and waves
Water temperature
tides
Avoid
Mod – high surf
Mod – strong current
Poor visibility
Kelp, nets, lines etc
Heavy surge
Overhead environments
Signals
Back and forth – help or emergency
Large circles – OK
Slowly waving up and down – attention
If you accidently hit the reef and drop your torch, make sure that you have not hurt yourself first. Examine your injury with your back-up light before attempting to retrieve your torch.
PEAK PERFORMANCE BUOYANCY
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 very important 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 regulator and deflate completely the BCD
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 when:
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 fresh water. 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 and it will drag your lower body down. More air will have to be added to the BCD to compensate and you will move less efficiently through the water
Underweighted and you will be swimming in a downward position as you will be constantly trying to compensate physically.
To change the buoyancy of an object that is neutral you can
Add or decrease weight
Decrease or increase volume or displacement
REACTIVATE
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 adult OW certification card
Upgrade Scuba Diver -as a refresher before the skills
Continuing Assessment - Assessment of divers readiness to continue
Certified Divers from Other Organisations - to refresh skills of divers from other organisation
SEARCH AND RECOVERY
• 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 prestreched 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 inflator so you can pull free easily and so it cannot tangle in rigging. After each burst, pull up to see if you can lift the object. Continue until object rises gently when you pull up and hovers off the bottom. You are trying to make it NEUTRALLY buoyant, not positively buoyant
• Do NOT lean over object as you will be in its path if it takes off suddenly. Important if stuck in mud bottoms as suction may be holding it down (rock object to help break suction)
• Once hovering, reinspect rigging. When ready to ascend, tow object horizontally along 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 liftbag
• Do not add air while ascending. Expanding air will increase buoyancy and bag and object will begin rising
• Either ascend with the object or let it ascend by itself. If bag capacity is close to objects 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 surface, add air to give plenty of positive buoyancy. You may tie to your float
SEARCH PATTERNS
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 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
Good visibility
Good for small to large objects.
Good over a variety of topography. Best over flat bottom but can be effective over uneven bottom or even current if done with care
Circular pattern
Need use of rope or line
Good in poor visibility
Need center point
Good on flat bottom for small objects in small area
Jackstay pattern
Covers a large area with poor visibility. 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 leg (or circle or length of pattern)
4 pulls come to me or let’s unite
continuous pulls emergency
KNOTS
Bowline
Generally recommended knot for making a reliable, easy-to-untie loop in a rope
Join two objects together. Easy to untie.
Doule half hitch
Tie a knot around an object
Sheetbend
Join two ropes together of different size
SMBs AND DSMBs
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 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.
SMB | DSMB |
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 |
WRECK
Salvage rights determine who owns something lost at sea. Different areas have different laws
Antiquity protection are 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
Hazards
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
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 analogue and digital compasses
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HEALTH AND SAFETY
EFR
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
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.
DETERMINING IF A PATIENT IS BREATHING
LOOK – Place the ear close to the patient’s mouth, turn your face to chest with your ear next to mouth and look to see chest 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 you hand on the patient’s chest
ALSO USED NOW FOR A CIRCULATION CHECK instead of looking for a pulse
RESCUE
Decompression Sickness
Inert gas forms bubbles in tissues and bloodstream as it comes out of solution due to high supersaturation following ascent
DCS can appear 15min 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 appear upon surfacing
Decompression Illness
Field term for both as first aid is the same for both decompression sickness and lung over-expansion injuries.
Upon surfacing Decompression Sickness occurs within a few hours and up to 36 hours
Lung Overexpansion occurs 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.
a
1. Treat all DCI as serious, even pain only DCS.
2. Give patient oxygen (preferably 100 percent) 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 left side, head supported (recovery position).
a. Helps keep airway clear if patient vomits.
b. Lying level helps ensure blood flow to brain.
c. Advise patient not to sit up or walk around, even during transport or if feeling better.
4. Lay non-breathing patient on back for rescue breathing/CPR.
5. Contact emergency medical care.
Types of systems.
positive pressure (beyond 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
TIRED DIVER | PANICKED DIVER |
Ask for help Respond to directions or questions Can assist in efforts to help Recover quickly | Overwhelmed by stress or fear Abandoned rational response React through instinct and fear Reject gear (mask on forehead, spitting out regulator or snorkel) Eyes wide Perceptual narrowing Does not respond to directions or questions Passive panic Failing to establish buoyancy |
In a panicked diver, perceptual narrowing is a decrease in the broad awareness through close focus on a perceived threat.
Your first concern should be getting that panicked diver buoyant.
Types of Diver Stress | |
Physical | Psychological |
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 boat or shore. An overexerting diver can feel air starved and fear that the regulator can’t deliver enough air.
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
*Survival rate of respiratory arrest is much higher than cardiac arrest
Brain damage occurs in as little as 4 – 6 minutes without oxygen in most instances. However, for reason not understood (especially in cold water), immersion can make revival possible even after long periods
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, still are 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 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.
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.
HEAT EXHAUSTION | HEAT STROKE |
Faint or dizz 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 |
HYPOTHERMIA | ADVANCED HYPOTHERMIA |
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 Jelly fish 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 a dive in warm tropical sea water and you 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
Not directly hazardous. Hazards come from impaired judgement and co-ordination, false sense of security, euphoria and 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,
SAFETY
BUDDY CHECKS - BWRAF
B – BCD/Buoyancy-
Check everything is connected and funcitoning. Test the inflate button and all the deflate valves. It is important to know how your buddys gear works in case of an emergency.
W – Weight
Ensure that each diver has their weights 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 any other places weights may need adjusting.
R – Releases-
Check each release is secure and you are familiar with the design. In case of 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 tank strap is in place to catch the tank if it slips the tank band 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 accidently turn the air off without a further safety step. THEN breath from regulator while looking at the
SPG or dive computer that is air-integrated. This will ensure that the tank is open and full, you gauge is working and the air tastes good. It can be helpfull to have both divers breathing at the same time from a single tank. One from the primary and one from the alternate , to see that they 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 reasons for cylinders slipping in nylon tank bands results from--adjusting the band while it is dry.
Make sure you check your own 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 procedurre for a safety stop is to do one on any dive below 10 mt/32 ft, at a depth of 5mt/15 ft for 3 minutes. This allows the divers 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 60 seconds. This is not a substitute for a safety stop at 5 mt but rather an additional stop 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
If you would like to test your knowledge on
Dive Skills and the Environment
Health and Safety
All the exams are together below
Would you like to test your knowledge on
Dive Skills and the Environment
The Environment You Dive
Do you want to check your knowledge on
Dive Skills and the Environment
Courses Part 1
Do you want to check your knowledge on
Dive Skills and the Environment
Courses Part 2
If you would like to test your knowledge on
Dive Skills and the Environment
Health and Safety
Nevin. (2022). A Guide to Decompression Stops – II. Scuba.com. https://www.scuba.com/blog/types-decompression-stops-ii/
DIVEIN.com. (2022, October 18). SMB or DSMB: What is a safety sausage really? - DIVEIN.com. DIVEIN. https://www.divein.com/diving/what-is-a-dsmb/
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)