Scuba diving fatalities


Scuba diving fatalities are deaths occurring while scuba diving or as a consequence of scuba diving. The risks of dying during recreational, scientific or commercial diving are small, and on scuba, deaths are usually associated with poor gas management, poor buoyancy control, equipment misuse, entrapment, rough water conditions, scuba depth record attempts, and pre-existing health problems. Some fatalities are inevitable and caused by unforeseeable situations escalating out of control, though the majority of diving fatalities can be attributed to human error on the part of the victim.
Equipment failure is rare in open circuit scuba, and while the cause of death is commonly recorded as drowning, this is mainly the consequence of an uncontrollable series of events taking place in water. Arterial gas embolism is also frequently cited as a cause of death, and it, too, is the consequence of other factors leading to an uncontrolled and badly managed ascent, possibly aggravated by medical conditions. About a quarter of diving fatalities are associated with cardiac events, mostly in older divers. There is a fairly large body of data on diving fatalities, but in many cases, the data is poor due to the standard of investigation and reporting. This hinders research that could improve diver safety.
For diving facilities, scuba diving fatalities have a major financial impact by way of lost income, lost business, insurance premium increases and high litigation costs.

Statistics

Diving fatality data published in Diving Medicine for Scuba Divers
  • 90% died with their weight belt on.
  • 86% were alone when they died.
  • 80% were men.
  • 50% did not inflate their buoyancy compensator.
  • 25% first got into difficulty on the surface.
  • 50% died on the surface.
  • 10% were under training when they died.
  • 10% had been advised that they were medically unfit to dive.
  • 5% were cave diving.
  • 1% of divers attempting a rescue died as a result.
Fatality rates of 16.4 deaths per 100,000 persons per year among DAN America members and 14.4 deaths per 100,000 persons per year the British Sub-Aqua Club members were similar and did not change during 2000–2006. This is comparable with jogging and motor vehicle accidents, and within the range where reduction is desirable by Health and Safety Executive criteria.
Activity-based statistics would be a more accurate measurement of risk. Noted above are statistics showing diving fatalities comparable to motor vehicle accidents of 16.4 per 100,000 divers and 16 per 100,000 drivers. DAN 2014/12/17 data shows there are 3.174 million divers in America. Their data shows that 2.351 million dive 1 to 7 times per year. 823,000 dive 8 or more times per year. It is reasonable to say that the average would be in the neighbourhood of 5 dives per year.
Data for 17 million student-diver certifications during 63 million student dives over a 20-year period from 1989-2008 show a mean per capita death rate of 1.7 deaths per 100,000 student divers per year. This was lower than for insured DAN members during 2000–2006 at 16.4 deaths per 100,000 DAN members per year, but fatality rate per dive is a better measure of exposure risk, A mean annual fatality rate of 0.48 deaths per 100,000 student dives per year and 0.54 deaths per 100,000 BSAC dives per year and 1.03 deaths per 100,000 non-BSAC dives per year during 2007. The total size of the diving population is important for determining overall fatality rates, and the population estimates from the 1990s of several million U.S. divers need to be updated.
During 2006 to 2015 there were an estimated 306 million recreational dives made by US residents and 563 recreational diving deaths from this population. The fatality rate was 1.8 per million recreational dives, and 47 deaths for every 1000 emergency department presentations for scuba injuries.
The most frequent known root cause for diving fatalities is running out of, or low on, breathing gas, but the reasons for this are not specified, probably due to lack of data. Other factors cited include buoyancy control, entanglement or entrapment, rough water, equipment misuse or problems and emergency ascent. The most common injuries and causes of death were drowning or asphyxia due to inhalation of water, air embolism and cardiac events. Risk of cardiac arrest is greater for older divers, and greater for men than women, although the risks are equal by age 65.
Several plausible opinions have been put forward but have not yet been empirically validated. Suggested contributing factors included inexperience, infrequent diving, inadequate supervision, insufficient predive briefings, buddy separation and dive conditions beyond the diver's training, experience or physical capacity.

Annual fatalities

  • DAN was notified of 561 recreational scuba deaths during 2010 to 2013. 334 were actively investigated by DAN
  • DAN was notified of 146 recreational scuba deaths during 2014. 68 were actively investigated by DAN
  • DAN was notified of 127 recreational scuba deaths during 2015. 67 were actively investigated by DAN
  • DAN was notified of 169 recreational scuba deaths during 2016. 94 were actively investigated by DAN
  • DAN was notified of 228 recreational scuba deaths during 2017. 70 were actively investigated by DAN
  • DAN was notified of 189 recreational scuba deaths during 2018.

    Cause of death

According to death certificates, over 80% of the deaths were ultimately attributed to drowning, but other factors usually combined to incapacitate the diver in a sequence of events culminating in drowning, which is more a consequence of the medium in which the accidents occurred than the actual accident. Often the drowning obscures the real cause of death. Scuba divers should not drown unless there are other contributory factors as they carry a supply of breathing gas and equipment designed to provide the gas on demand. Drowning occurs as a consequence of preceding problems, such as cardiac disease, pulmonary barotrauma, unmanageable stress, unconsciousness from any cause, water aspiration, trauma, equipment difficulties, environmental hazards, inappropriate response to an emergency or failure to manage the gas supply.
The data gathered in relation to the actual causes of death is changing. Although drowning and arterial gas embolisms are cited in the top three causes of diver deaths, stating these as solitary causes does not recognise any pre-existing health issues. Researchers may know the actual causes of death, but the sequence of events that led to the cause of death is often not clear, especially when local officials or pathologists make assumptions.
In many diving destinations, resources are not available for comprehensive investigations or complete autopsies, The 2010 DAN Diving Fatalities workshop noted that listing drowning as a cause of death is ineffective in determining what actually occurred in an incident, and that lack of information is the primary reason for personal injury lawsuits filed in the industry.
A DAN study published in 2008 investigated 947 recreational open-circuit scuba diving deaths from 1992–2003, and where sufficient information was available, classified the incidents in terms of a sequence of trigger, disabling agent, disabling injury and cause of death. Insufficient gas was the most frequent trigger, at 41%, followed by entrapment at 20%, and equipment problems at 15%. The most common identifiable disabling agents were emergency ascents, at 55%, followed by insufficient gas at 27% and buoyancy complications at 13%. The most frequent disabling injuries were asphyxia at 33%, arterial gas embolism at 29% and cardiac incidents at 26%. Cause of death was reported as drowning in 70% of the cases, arterial gas embolism in 14% and cardiac arrest in 13%. The investigator concluded that disabling injuries were more relevant than cause of death, as drowning often occurred as a consequence of a disabling injury. A further analysis linked risk of type of disabling injury with trigger events. Asphyxia followed entrapment, insufficient gas, buoyancy problems, equipment problems, rough water. Arterial gas embolism was associated with emergency ascent, insufficient gas, equipment trouble, entrapment. Cardiac incidents were associated with cardiovascular disease and age over 40 years. Their conclusion was that the most effective way to reduce diving deaths would be by minimising the frequency of adverse events.

Manner of death

If the manner of death is deemed to be accidental, which is usually the case, the incident leading to death is seldom analysed sufficiently to be useful in determining the probable sequence of events, particularly the triggering event, and therefore is not usually useful for improving diver safety.
The chain of events leading to diving fatalities is varied in detail, but there are common elements: a triggering event, which leads to a disabling or harmful event and causes a disabling injury, which may itself be fatal or lead to drowning. One or more of the four events may not be unidentifiable.
Death usually followed a sequence or combination of events, most of which may have been survivable in isolation. In the more than 940 fatality statistics studied by DAN over ten years, only one-third of the triggers could be identified. The most common of these were:
  1. Insufficient gas
  2. Entrapment
  3. Equipment problems
Disabling agents were also identified in one-third of the cases. The most common identified were:
  1. Emergency ascent
  2. Insufficient gas
  3. Buoyancy trouble
  4. Excessive work of breathing

    Disabling injuries

Disabling injuries were identified in nearly two-thirds of the cases. The criteria for identify the disabling injury by forensic judgement are specified.
  1. Asphyxia, with or without aspiration of water, and no evidence of a previous disabling injury.
  2. *Triggering events associated with asphyxia included:
  3. ** entrapment due to entanglement in kelp, wreckage, mooring lines, fishing lines or nets, and entrapment in confined spaces or under ice
  4. ** insufficient gas, when it was the first identifiable problem, but generally the reason for lack of gas was not determined.
  5. ** problems with equipment included regulator free-flow, unexpectedly high gas consumption, and diver error in the use of the scuba apparatus, buoyancy compensator, weighting system or dry suit.
  6. ** rough water conditions included high sea states, strong currents, and surf conditions at beaches, rocky shores and piers.
  7. * Disabling agents associated with asphyxia cases included:
  8. ** insufficient gas, triggered by entrapment, equipment problems, or high gas consumption due to heavy exercise in rough conditions.
  9. ** buoyancy problems, triggered by over- or under-weighting, lack of inflation gas for the buoyancy compensator, or over-inflation of the buoyancy compensator or dry suit.
  10. ** emergency ascent, triggered by entrapment or lack of breathing gas, was associated with both asphyxia and lung overpressure injury.
  11. * Other contributing factors were not as clearly connected: Panic was reported in about a fifth of the cases, and may have caused aspiration or accelerated gas consumption. Casualties were diving alone or were separated from their buddies in about 40% of cases with asphyxia, but this was also associated with other disabling injuries.
  12. Arterial gas embolism, with gas detected in cerebral arteries, evidence of lung rupture, and history of an emergency ascent.
  13. * Triggers associated with AGE included:
  14. ** insufficient gas,
  15. ** equipment problems,
  16. ** entanglement or entrapment
  17. * AGE deaths were often associated with panic.
  18. * Disabling agents associated with AGE cases included:
  19. ** emergency ascent. Loss of consciousness was typical, followed by drowning for divers who remained in the water after surfacing.
  20. Cardiac incidents, where chest discomfort was indicated by the diver, distress displayed with no obvious cause, a history of cardiac disease and autopsy evidence.
  21. * There were few overt triggers or disabling agents identified, but reports suggested that about 60% of the decedents displayed symptoms of dyspnea, fatigue, chest pain or other distress, and 10% displayed these symptoms before the dive.
  22. * Problems were noticed before entering the water in 24% of these cases, at the bottom in 46% of cases, and after starting the ascent in 20% of cases
  23. * Loss of consciousness could occur at any time.
  24. * Autopsy reports usually showed evidence of significant cardiovascular disease but seldom myocardial damage, which suggests that fatal dysrhythmias or drowning may have occurred before heart muscle injury could develop.
  25. * Disabling cardiac incidents were associated with cardiovascular disease and age greater than 40 years, but no significant association with body mass index.
  26. Trauma, where a traumatic incident was witnessed or determined by autopsy. The cause of injury is usually obvious, and included incidents of being struck by a watercraft, tumbled over a rocky shoreline by surf, electric shock, and interactions with marine animals. Some could possibly have been avoided by the diver. Traumatic injuries were most commonly associated with rough water conditions and being a frequent diver.
  27. Decompression sickness, based on symptoms, signs and autopsy findings. Triggers for DCS included:
  28. * insufficient gas, followed by emergency ascent with omitted decompression.
  29. * multiple repetitive dives with short surface intervals.
  30. * gas lost in a regulator free-flow
  31. * uncontrolled ascent due to dry suit inflator malfunction
  32. * dragged deep by a speared fish
  33. * DCS was associated with deep diving, diving alone, and emergency ascent with omitted decompression
  34. Unexplained loss of consciousness, where the diver was discovered unconscious without obvious cause.
  35. * Triggers may have included deep dives, diabetes and nitrox dives, including a seizure witnessed at a depth where the oxygen partial pressure would have been approximately 1 bar, normally considered safe.
  36. * Loss of consciousness was associated with diabetes, frequent diving, and learner divers.
  37. Inappropriate gas, Breathing gas supply contaminated by toxic levels of carbon monoxide, or selection of gas with excessive or insufficient oxygen content for the depth.
  38. * CNS oxygen toxicity, in some cases associated with medications.
  39. * Carbon monoxide poisoning from contaminated cylinder gas
  40. * Hypoxia, from incorrect gas choice and from oxygen content depleted by corrosion in the cylinder