List of Diving Hazards and Precautions - The Specific Diving Environment

The Specific Diving Environment

Hazard	Consequences	Cause	Avoidance and prevention
Exposure to cold water during a dive, and cold environment before or after a dive, wind chill.	Hypothermia: Reduced core temperature, shivering, loss of strength, reduced level of conscuousness, loss of consciousness and eventually death.	Loss of body heat to the water or other surroundings. Water carries heat away far more effectively than air. Evaporative cooling on the surface is also an effective mechanism of heat loss, and can affect divers in wet diving suits while travelling on boats.	Diving suits are available which are suited to a wide range of water temperature down to freezing. The appropriate level of insulation for the conditions will reduce heat loss. In extreme conditions and when helium based mixtures are in use as breathing gas, heated suits may be necessary. On the surface, wind chill can be avoided by staying out of the wind, staying dry, and suitable protective clothing. Some parts of the body, particularly the head, are more prone to heat loss and insulation of these areas is correspondingly important.
	Nonfreezing Cold Injuries (NFCI).	Exposure of the extremities in water temperatures below 12°C (53.6°F)	Hand and Foot Temperature Limits to avoid NFCI: Fully Functional 18°C (64.4°F) Non Freezing Cold Injury Threshold < Week. 12°C (54°F) approximately 3 hours. 8°C (46.4°F) for maximum of 30 min. 6°C (42.8°F) immediate rewarming required. Protection in order of effectiveness: Dry gloves attached to drysuit without wrist seal. Dry gloves with wrist seal. Wet suit (neoprene) gloves. Rubberised cloth or leather gloves.
	Muscular cramps	Inadequate insulation Reduced perfusion to the legs and feet (occasionally hands)	Better insulation and/or suit fit
Hard corals	Coral cuts - Infected lacerations of the skin.	Sharp coral skeleton edges lacerating or abrading exposed skin, contaminating the wound with coral tissue and pathogenic microorganisms.	Coral cuts may be prevented by avoiding contact of unprotected skin with coral. Protective clothing such as wet-suit, dry suit, skin/lycra suit or overalls are effective.
Sharp edges of rock, metal, etc.	Lacerations and abrasions of the skin, possibly deeper wounds.	Contact with sharp edges.	Most cuts may be avoided by wearing protective clothing such as wet-suit, dry suit, skin/lycra suit or overalls. Avoiding high risk areas such as shipwrecks during strong water movements such as surge or currents is also effective. Strength and skill in avoiding contact with sharp edges will help, but does not eliminate the risk when water movement is strong.
Stinging hydroids.	Stinging skin rash, local swelling and inflammation	Contact of bare skin with fire coral	Avoid contact with benthic organisms. Protective clothing such as exposure suits, lycra skins, or overalls are effective.
Stinging jellyfish	Stinging skin rash, local swelling and inflammation, sometimes extremely painful, occasionally dangerous or even fatal	Some species of jellyfish (free swimming cnidaria) have stinging cells which are toxic to humans, and will inject venom on contact with the skin.	Avoid contact with jellyfish tentacles. Protective clothing such as exposure suits, lycra skins, or overalls is effective.
Stingrays	A deep puncture or laceration which leaves venom in the wound	Defensive reaction of a sting ray when disturbed or threatened, by lashing out with the venomous spine on the tail.	Stingrays can usually be avoided by not poking about on the bottom where they may be hiding, partly or completely buried under a thin layer of sand. The risk is usually greater when wading, when the wader may inadvertently step on a buried ray. Rays are usually very shy and will usually swim away when approached Risk of injury may be avoided by not molesting or threatening the animals when seen, and by staying a safe distance from the tail
Tropical reef environment	Reef rash: General or localised stinging or inflammation of the skin. may include allergic reactions.	A generic catch-all term that refers to the various cuts, scrapes, bruises and skin conditions that result from diving in tropical waters. This may include sunburn, mild jellyfish stings, sea lice bites, fire coral inflammation and other skin injuries that a diver may get on exposed skin.	A full-body exposure suit can prevent direct skin to environment contact.
Fish and invertebrates with venomous spines.	Puncture wounds with venom injection. Often extremely painful and may be fatal in rare cases.	Lionfish, stonefish, crown of thorns starfish, some sea urchins in warm seas	Most of these animals are sedentary and non-aggressive and may be avoided if seen and recognised in time. The risk is often greater when wading. Some protection is provided by rubber soled neoprene diving boots, but hard soled boots are more effective.
Venomous octopus	Local envenomation at site of bite wound. Extremely painful and may result in death.	The Blue ringed octopus may on rare occsions bite a diver.	Found only in parts of the Pacific Ocean from Japan to Australia. The octopus is unlikely to be aggressive, and is not likely to bite unless handled. However it can be well camouflaged against the reef and difficult to see, so not contacting the reef is the most reliable way to avoid contact.
Sharks	Lacerations by shark teeth can involve deep wounds, loss of tissue and amputation, with major blood loss. In extreme cases death may result,	Attack or investigation by shark with bites. Risk is location, conditions, and species dependent.	Consult location-specific information to determine risk. Never molest even apparently docile sharks underwater.
Crocodiles	Lacerations and punctures by teeth, brute force tearing of tissues. Possibility of drowning.	Crocodiles, in some tropical waters	Consult local information on risk. Stay out of waters known to be inhabited by crocodiles.
Titan triggerfish	(description of injury to go here)	This tropical Indo-Pacific fish is very territorial during breeding season and will attack and bite divers	Keep a lookout for the fish and move away if they act aggressively.
Very large groupers.	Bite wounds, bruising and crushing injuries.	The Giant 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.	Get local information on risk. Stay clear of very large specimens. Do not attempt to feed the fish, they may take more than is offered.
Electric shock	Electrical discharge that will startle and may stun the diver	Defense machanism of Electric eel, in some South American fresh waters	Get local information on risk. Do not touch the animals if seen.
		Defense mechanism of Electric ray, in some tropical to warm temperate seas	Do not touch the animal.
		It is said that some naval anti-frogman defences use electric shock	Keep out of armed forces areas
Powerful ultrasound	(description of injury to go here)	It is said that some naval anti-frogman defences use powerful ultrasound. Also used for long-range communication with submarines Most high power sonar is used for submarine detection and target acquisition.	Keep out of armed forces areas. Avoid large naval ships' anti-submarine warfare sonar. See Underwater Port Security System.
Water contaminated by infectious aquatic organisms	Weil's disease	Leptospirosis infection (Weil's disease) is commonly transmitted to humans by allowing water that has been contaminated by animal urine to come in contact with unhealed breaks in the skin, the eyes, or with the mucous membranes. Outside of tropical areas, leptospirosis cases have a relatively distinct seasonality with most of them occurring in spring and autumn.	Avoid diving in contaminated water. Analyse water before diving if presence of contaminants is suspected, but type and concentration is not known. If it is necessary, and depending on risk: A watertight drysuit with dry gloves and integral dry hood, and positive pressure full face diving mask will provide acceptable protection in some circumstances. Surface supplied equipment with heavy duty full environmentally sealed dry suit with integral boots and gloves, and helmet sealed to suit, with either free flow air supply or series exhaust valve system will provide more protection. Gas reclaim systems can provide the greatest security to ingress of contaminants. The gas need not actually be reclaimed if it is not economically desirable, the systems are used so that there are no potential leaks though underwater exhaust openings. Protective overalls may be worn over the drysuit to protect it from puncture damage. Appropriate decontamination procedures may be used after the dive. The diver should breathe from the diving air supply when surfaced in environments where air quality is uncertain.
	Bilharzia (in some warm fresh water)	Schistosomiasis (bilharzia) is a parasitic disease caused by several species of trematodes or "flukes" of the genus Schistosoma. Snails serve as the intermediary agent between mammalian hosts. This disease is most commonly found in Asia, Africa, and South America, especially in areas where the water contains numerous freshwater snails, which may carry the parasite. The parasitic larvae enter through unprotected skin and further mature within organ tissues.
	(details to come)	Various bacteria found in sewage
Chemically polluted water	Consequences variable depending on: Identity of pollutant Concentration of pollutant Exposure to pollutant Refer to Materials Safety Data Sheet (MSDS) for identified pollutants.	Water polluted by industrial waste outfalls or by natural sources.
Hydrogen sulfide	Hydrogen sulfide poisoning: (Concentrations are listed at normal atmospheric pressure. 1000 ppm at 1 bar is equivalent to a partial pressure of 1 mbar) 0.0047 ppm is the recognition threshold, the concentration at which 50% of humans can detect the characteristic odor of hydrogen sulfide, normally described as resembling "a rotten egg". Less than 10 ppm has an exposure limit of 8 hours per day. At 100–150 ppm the olfactory nerve is paralyzed after a few inhalations, and the sense of smell disappears, often together with awareness of danger. 320–530 ppm leads to pulmonary edema with the possibility of death. 530–1000 ppm causes strong stimulation of the central nervous system and rapid breathing, leading to loss of breathing. 800 ppm is the lethal concentration for 50% of humans for 5 minutes exposure (LC50). Concentrations over 1000 ppm cause immediate collapse with loss of breathing, even after inhalation of a single breath.	Hydrogen sulfide is associated with sour natural gas, crude oil, anoxic water conditions and sewers (more information needed). hydrogen sulfide is present in some lakes and caves and can also be absorbed through the skin.
Impact with boat or shoreline	Broken bones, bleeding, lacration wounds and other trauma	Colliding with a boat or its propeller. Wave action on rocky shore.	Use of Surface detection aids or a diving shot to locate and mark surfacing position and warn vessels of the presence of divers. A safe exit point and alternatives may be planned for taking into account forecasts for weather and tidal conditions.
Abandonment at surface after a boat dive	Diver lost at sea on the surface after a dive, with risk of exposure, drowning and dehydration.	Diver separated from boat cover due to poor visibility at surface or strong underwater currents. Diver left behind due to inaccurate check by boat crew. Diver unable to return to unattended boat.	Boat crew may use a positive check system to identify that each diver is on board after a dive. Divers may carry a yellow flag or surface marker buoy to attract attention. Divers may carry a personal submersible EPIRB or vhf radio. Divers may carry a signalling mirror and/or sound signalling device. Diving form unattended boats only when a safe shore exit is feasible.
Inability to return to shore or to exit the water	Diver lost at sea after a shore dive	Big breaking waves make it unsafe to approach the shore Currents move the diver away from a safe exit Weather conditions make the sea too rough to safely exit.	Local knowledge, good weather forecasts, plan alternative exits. EPIRB, marker buoy, flares, die markers, signalling light, mirror, whistle or other means of signalling distress and indicating position to rescuers. Good buoyancy aids and exposure suit to provide protection while rescue is awaited. Notification before the dive of someone on shore of the expected time of return, so they can notify the rescue orgabisations if the divers do not return within a reasonable time.
Silt	Sudden loss of underwater visibility (silt out) which can cause disorientation and a diver getting lost under an overhead.	Stirring up silt or other light loose material, either by natural water movement or by diver activity, often due to poor trim and finning skills.	Appropriate trim, buoyancy and propulsion techniques. Training and skills for diving in zero visibility and silting risk areas. Use of distance line when it is possible to end up under an overhead.
Entrapment hazards such as nets, lines, kelp, unstable structures or terrain, and confined spaces.	Diver trapped underwater and may run out of breathing gas and drown. Inappropriate response due to panic is possible.	Snagging on lines, nets, wrecks, debris or in caves. Entrapment by collapse of terrain or structure, either directly or by obstructing the exit route.	Carrying at least one effective line cutting implement, more in high risk areas. Diving with a buddy who is capable of helping to free the trapped diver and will stay close enough to notice. Training in wreck diving and cave diving techniques. Use of low snag equipment configurations (avoid dangling gear and snap hooks that can snag on lines).
Overhead environment (cave, wreck or ice, where direct ascent to the surface is obstructed)	Diver may get lost and be unable to identify the way out, and may run out of breathing gas and drown. Inappropriate response due to panic is possible.	Getting lost in wrecks and caves or under ice where there is no direct route to the surface, often due to not using a distance line, or losing it in darkness or bad visibility, but sometimes due to the line breaking.	Appropriate training and dive planning. Correct use of reels, lines and directional markers. Backup lights.
Strong currents or surge	Impact against the bottom terrain or underwater structures, which can dislodge equipment such as mask or DV, roll off a cylinder valve, snag and damage equipment or cause impact trauma to the diver. Severity can vary from annoyance to fatal. It is also possible to get wedged into a small gap and trapped, or caught up on nets or lines in the water. In an overhead environment the diver may be unable to get back against a strong current.	Strong water movement carrying the diver along and into contact with rigid objects fixed in place. Strong water movement creating so much drag on the diver that progress upcurrent is severely restricted.	Strong currents and surge may often be avoided by planning the time of the dive. Divers may stay a safe distance from the bottom terrain during drift dives. Drift divers may tow a surface marker buoy to identify their positions to the boat.
Breaking waves (surf)	Impact injury and damage to equipment. Disorientation. Loss of equipment, temporary loss of breathing gas.	Uncontrolled transportation by surf surge onto rocks or other hard obstacles. Tumbling in breaking wave cusing vertigo. Strong turbulence in breaking wave may pull equipment from diver, particularly mask and demand valve, occasionally fins.	Avoidance of strong surf transits. Minimising time in surf zone. Secure attachment of equipment. Protection of mask and demand valve security by holding them in place in high turbulence.
Low visibility and darkness. (in conjunction with other hazards)	Inability to read instruments to monitor depth, time, ascent rate, decompression schedule, gas pressure, and to navigate. These are not dangerous in themselves, but may result in the diver getting lost, swimming into an entrapment hazard or under an overhang, violating a decompression obligation, or running out of breathing gas.	Lack of light or absorption of light by turbidity.	A dive light can provide light if the visibility is sufficient. In zero visibility special precautions must be taken. It is usually preferable to use surface supplied equipment with voice communications, as the diver can not get lost, and the surface team can monitor depth, time, breathing gas and decompression obligations. Navigation and work must be done by feel.
High altitude	Increased risk of decompression sickness - Reduced ambient pressure can induce bubble formation or growth in saturated tissues.	Diving at altitude.	Acclimatisation at altitude before diving. Use of decompression schedules designed for altitude diving.
High altitude		Ascent to altitude after diving, including: Flying in pressurised aircraft. Flying in unpressurised aircraft. Ascent by road or rail to significantly higher altitude.	Surface interval appropriate to the planned change in altitude.

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