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Diving hazards and precautions

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Divers face specific physical and health risks when they go underwater (e.g. with scuba or other diving equipment) or use high pressure breathing gases. Some of these conditions also affect people who work in raised pressure environments out of water, e.g. in caissons.

According to a North American 1970 study, diving was (on a man-hours based criteria) 96 times more dangerous than driving an automobile.[1]According to a 2000 Japanese study, every hour of recreational diving is 36 to 62 times riskier than automobile driving.[2]


The ordinary features of diving

Click on the boldface links for more information about each topic.

Need to:RemedyComments
Breathe underwaterOpen-circuit scuba setEasy to refill. Safer to use than a rebreather.
RebreatherLonger duration per weight of set, but needs more training to be safe.
Surface supplied divingMostly for work diving
Standard diving dressMostly for work diving. Mostly merely of historical interest now.
Liquid breathing systemTheoretical only; no working system has yet been developed, but could allow very deep diving if a practical system were to be developed.
See underwater.
Protect the eyes.
(The human eye cannot focus accurately when directly submerged.)
Eyes-and-nose diving maskEasy to clear if flooded. Easily knocked off.
Full face maskAllows talking if no mouthpiece inside.
Difficult or impossible to go to snorkel on surface.
Diving helmetAs fullface mask. Protects the head well.
Special contact lensesOccasionally used by commando frogmen instead, to avoid searchlight beams reflecting off a mask window.
Move faster than
with unequipped swimming
Fins on feetCheap, easy to use. Closed heel for skin diving, open heel with bootees for scuba diving. Sometimes bootees are worn without the rest of a wetsuit to let the diver wear bigger fins.
Diver Propulsion VehiclesFaster but expensive, heavy and bulky to carry about on land. Hazardous unless used by experienced divers as it makes it easy to become lost or to exceed the range of safe return by swimming alone in the event of vehicle failure.
Avoid hypothermia (losing
body heat to the water)
In cool or cold water, wear an adequately warm diving suit for the conditions.Much heat can be lost from a head without a hood.
Control buoyancyDiving weighting systemsUsually a weight belt. Some breathing sets have built-in weight pouches.
Diving suitsThe buoyancy of most drysuits can be changed during the dive.
Buoyancy compensatorsThese make diver's buoyancy control much easier.
Protect the skin from cuts and stings and grazesDiving suits and diving gloves and diving suit bootees serve this purpose.In very warm water try diving in a boiler suit, or other strong clothes with long sleeves and legs.
Breathe from atmosphere to save air when on surfaceSnorkelAdvisable, despite some naval divers' opinions.

Effects of relying on breathing equipment while underwater

Being unable to breathe fresh air naturally whilst submerged and relying on limited breathing gas supplies and fallible breathing equipment can have these effects. Click on the boldface links to find symptoms and more information for each topic.

Types of this sort of diving disorder, and how to avoid them
TypeCauseHow to avoid it
DrowningBeing unable to inhale anything but waterSee under "anoxia" hereinunder
Secondary drowningCan occur hours after a near drowningPrompt medical treatment after near drowning
Oxygen toxicityBreathing gas at too high a partial pressure of oxygen; partial pressure depends upon proportion of oxygen and depthProper training before using a rebreather or oxygen enriched gases such as nitrox.
Hypoxia or anoxia occurs while having gas to breathe, but where the oxygen partial pressure is too low to sustain normal activity or consciousness.A faulty or misused rebreather can provide the diver with hypoxic gasKeep rebreathers properly maintained.
Proper training before using a rebreather.
Some deep diving breathing gases such as trimix and heliox can be hypoxicDon't breathe hypoxic gas in shallow water.
Proper training before using mixed gases.
A full cylinder standing for a long time while the inside of the cylinder rusts, using up oxygen in the contained air, before the diver uses the cylinderKeep cylinders routinely checked and tested. If a cylinder has stood full for months, empty it and refill it.
Anoxia due to having no air or gas to breatheEquipment failure - particularly in rebreathers that monitor and maintain oxygen contentKeep equipment routinely checked and in good condition
Running out of air due to a number of factors, including poor dive disciplineBetter training of divers. More disciplined attitude when underwater.
Running out of air due to getting trapped by netsBetter awareness underwater. Carry a diver's net cutter, or dive tool/knife.
Running out of air due to getting trapped or lost in enclosed spaces underwater (e.g. caves and shipwrecks)Specific training and leadership for such types of diving. See cave diving and wreck diving.
Running out of air due to getting lost in open waterBetter training and leadership, including in using a compass underwater
Salt water aspiration syndromeInhaling a mist of sea water from a faulty demand valve causing a reaction in the lungsKeep equipment routinely checked and in good condition
Carbon monoxide poisoningAir cylinder filled by a compressor which sucked in products of combustion, often its own engine's exhaust gasProper precautions when filling cylinders
Oil getting into the air feed and firing in the air compression cylinder, like in a diesel engineProper servicing of the compressor
Emphysema caused by inhaling oil mistThis happens gradually over a long time. This is a particular risk with a pumped surface air feed.Use proper filters in the air pump or air compressor.
Carbon dioxide poisoning: hypercapniaRe-inhaling carbon dioxide-laden exhaled gasMinimise the volume of any enclosed spaces which the diver breathes through. For example, this hazard can happen with diving with a large "bubblehead" helmet.
With a rebreather, the diver re-inhales carbon dioxide because the soda lime scrubber cannot absorb the exhaled carbon dioxide as fast as the diver produces it. See Rebreather#Carbon dioxide scrubber.British naval divers called it shallow water blackout. Keep rebreathers properly maintained. Proper training before using a rebreather.
Various effects of breathing a wrong gasA wrong gas was put in a cylinderCheck conditions where you have your cylinders refilled. Put the proper gas identification markings on cylinders.

Effects of barotrauma or pressure damage

See barotrauma and pressure for more information.

On descent

Air spaces within the body provide no support against greater outside pressure. This can happen from losing control of buoyancy causing excessive vertical speed during descent. Click on the boldface links to find symptoms and more information for each topic.

Types of this sort of diving disorder, and how to avoid them
TypeCauseHow to avoid it
Eardrum damage. Cold water in the middle ear chills the inner ear, causing dizziness and disorientation etc.Failing to equalize the pressure in the middle ear with surrounding pressure.Do not dive if the eustachian tube is congested, e.g. with the common cold.
Proper diver training in clearing the ears.
The pressure in the outer ear not equalizing with surrounding pressureMake sure that your hood does not make an airtight seal over the outside ear hole; never wear earplugs.
Damage to other body air spaces, such as the paranasal sinuses.Obstruction to the sinus ductsDo not dive with conditions such as the common cold
Squeeze damage to blood vessels around the eyesCaused by suction from the air space inside a mask ("mask squeeze") which is not a fullface maskLet air into the mask through the nose. Do not dive with eyes-only goggles.
Squeeze damage to skin under folds in a drysuitSuction into the space inside the foldModern drysuits have a tube connection to inflate the drysuit from the cylinder
Lung squeeze: blood in lungsExtreme depth when snorkellingUse an underwater breathing set
Helmet squeeze, with the old standard diving dress. This does not happen with scuba where there is no solid pressure-tight helmetA valve in the helmet failing. In severe cases much of the diver's body could be mangled and compacted inside the helmet[dubious ]Keep equipment in good order and inspected. Proper training in its use.

On ascent

Air spaces within the body expand when the outside pressure decreases. This can happen from holding the breath on ascent, or from losing control of buoyancy causing excessive vertical speed during ascent. Click on the boldface links to find symptoms and more information for each topic.

Types of this sort of diving disorder, and how to avoid them
TypeCauseHow to avoid it
Pulmonary barotrauma: "burst lung"Holding the breath while ascendingNever hold your
breath while diving
with breathing
apparatus
This can cause:
PneumothoraxCollapsed lung, air loose in the pleural cavity
Interstitial emphysemaGas trapped in the chest after burst lung
Subcutaneous emphysemaGas loose under the skin.
Gas embolismAir or other gas in the blood stream.
Its effects can be very similar to decompression sickness.
Pain in a sinusBlockage of the sinus's ductDo not dive with nasal congestion,
e.g. the common cold.
Eardrum bursting outwardsBlocked Eustachian tube

Effects of breathing gas at high pressure

Click on the boldface links to find symptoms and more information for each topic.

Types of this sort of diving disorder, and how to avoid them
TypeCauseHow to avoid it
Decompression sickness ("the bends")Gas dissolves in blood under pressure according to Henry's Law over time. After dive, ascending too quickly will cause gas to supersaturate and form bubbles in tissues according to time and depth of the dive.Plan your dive. Know how long you can stay at the planned depth and still make a normal ascent. If stops are necessary, do not miss or cut short decompression stops. Training in using diving tables and a dive computer. See decompression sickness for a detailed list of the symptoms. Provide something for the diver to hold onto while decompressing.
Bends in snorkellers. Uncommon but known.Many deep dives in succession. See taravana.Use an underwater breathing set
Nitrogen narcosisBreathing a high partial pressure of nitrogen (or other inert gas, to varying degrees)Do not dive too deep on ordinary air. With mixture diving, use the correct breathing gas.
Oxygen toxicityBreathing a high partial pressure of oxygenThis hazard is well known with rebreathers.
This can happen in very deep diving with open-circuit scuba.
HPNS: High Pressure Nervous Syndrome or Helium TremorsBreathing a high partial pressure of heliumUse another diving technique, such as an ROV; or add a little nitrogen as described at HPNS.

The term dysbarism describes Decompression sickness, arterial gas embolism, and barotrauma.

Divers face specific physical and health risks when they go underwater (e.g. with scuba) or use high pressure breathing gases. Some of these conditions also affect people who work in raised pressure environments out of water, e.g. in caissons.

Other risks encountered by people in water

Types of this class of diving disorder, and how to avoid them. Click on the boldface links to find symptoms and more information for each topic.
Where it says "Avoid diving with bare skin", a boilersuit could be worn in very warm water.
TypeCauseHow to avoid it
HypothermiaLosing body heat to the water. Water carries heat away far better than air.In cool or cold water, wear an adequately warm diving suit for the conditions. Also, much heat can be lost from a head without a hood.
Cuts, sometimes with coral tissue left in themCoralDo not get too close to coral.
Avoid diving with bare skin.
CutsRock, metal, etcAvoid diving in bare skin, particularly in caves or shipwrecks.
StingsFire coralIt is yellow. Learn to identify it.
Stings, some dangerousSome jellyfishLearn about the dangerous species.
Avoid diving with bare skin.
A deep cut which leaves poison in the woundsting ray (its self-defence reaction)Do not poke about in sand where they live.
Care when wading.
Reef rashA generic catch-all term that refers to the various cuts, scrapes, bruises and skin conditions that result from diving in tropical waters. This includes sunburn, jellyfish stings, sea lice bites, fire coral inflammation and other skin injuries that a diver may gain from using a shorty wetsuit or no diving suit.Wear a full-body exposure suit to prevent direct skin to environment contact.
Poison-injecting spineslionfish, stonefish, crown of thorns starfish, some sea urchins in warm seasLearn to identify them. Keep away from them.
Care when wading.
Poison injectionBlue ringed octopus, in parts of the Pacific Ocean
Shark bitesSharks, likelihood of risk is location dependentConsult location-specific information to determine risk; never molest even seemingly-tame sharks underwater.
Crocodile attackCrocodiles, in some tropical watersGet proper information on them
Attack by an unusually large grouper.Epinephelus lanceolatus can grow very big in tropical waters, where protected from attack by sharks. There have been cases of very large groupers trying to swallow humans.[3][4][5][6][7]Get proper information on them.
ElectrocutionElectric eel, in some South American fresh waterGet proper information on them
Electric ray, in some warm seas
It is said that some naval anti-frogman defences use electric shockKeep out of armed forces areas
Powerful ultrasoundIt is said that some naval anti-frogman defences use powerful ultrasound. Also used for long-range communication with submarinesKeep out of armed forces areas.
Avoid large ships' ordinary sonar.
See Underwater Port Security System.
Exposure to disease carried by in-water organismsWeil's disease (in rat's urine)
Bilharzia (in some warm fresh water)
Various bacteria found in sewage
In affected water, dive in watertight drysuit and full face diving mask
Exposure to harmful chemicals in the waterMay be found in water polluted by industrial waste outfalls or by natural sources. For example hydrogen sulfide in some lakes and caves can be absorbed through the skin.
Broken bones, bleeding wounds and other traumaColliding with a boat or its propellor.
Wave action on the shore.
Use Surface detection aids or a diving shot to mark surfacing position and aid searchers. Plan a safe exit point and check weather and tidal conditions.
Diver lost at sea after a boat diveSeparated from boat cover due to poor visibility at surface or strong underwater currents.
Diver lost at sea after a shore diveBig waves made it unsafe to leave the water; currents moved the diver away from a safe exit; surface weather on the shore make the sea too rough to safely exit.
Sudden loss of underwater visibilitySilt out: stirring up silt or other light loose materialTraining in diving in zero visibility. Learn the frog kick.

See also

References

  1. ^ Lansche, James M (1972). [Expression error: Missing operand for > "Deaths During Skin and Scuba Diving in California in 1970"]. California Medicine 116 (6): 18–22. 
  2. ^ Ikeda, T; Ashida, H (2000). "Is recreational diving safe?". Undersea and Hyperbaric Medical Society. http://archive.rubicon-foundation.org/6770. Retrieved 2009-08-08. 
  3. ^ Alevizon, Bill (July 2000). "A Case for Regulation of the Feeding of Fishes and Other Marine Wildlife by Divers and Snorkelers". Reef Relief. http://www.reefrelief.org/science_body4.shtml. Retrieved 2009-08-08. 
  4. ^ Allard, Evan T (2002-01-04). "Did fish feeding cause recent shark, grouper attacks?". Cyber Diver News Network. http://www.cdnn.info/eco/e020104/e020104.html. Retrieved 2009-08-08. 
  5. ^ "Goliath grouper attacks". Jacksonville.com (Florida Times-Union). 2005-06-19. http://www.jacksonville.com/tu-online/stories/061905/spo_19030958.shtml. Retrieved 2009-08-08. 
  6. ^ Sargent, Bill (2005-06-26). "Big Grouper Grabs Diver On Keys Reef". FloridaToday.com. Florida Museum of Natural History. http://www.flmnh.ufl.edu/fish/InNews/grouperattack2005.html. Retrieved 2009-08-08. 
  7. ^ Arthur C. Clarke, Reefs of Taprobane, ISBN 0-7434-4502-3, page 138: 15 feet long, 4 feet side side to side. in the sunken Admiralty floating dock in Trincomalee, Sri Lanka

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