Is Scuba Diving Dangerous? Death Rates, Causes and Who Is at Risk

What is the scuba diving death rate?

Most published rates fall between about 2 and 20 deaths per 100,000 divers a year, and the spread comes mostly from who gets counted. DAN's 2016 Annual Diving Report set the 2014 death count against an industry estimate of more than 3,000,000 US scuba participants and concluded that around 2 of every 100,000 US recreational divers die while diving each year. DAN called the figure imprecise, because it could not tell how many participants died abroad or how many US deaths were visitors. It also noted that the number has stayed fairly stable over time.

The higher figures come from groups with a known membership list. Among DAN members who held dive accident insurance from 2000 to 2006, there were 187 diving deaths in 1,141,367 member-years: 16.4 per 100,000 a year on average, with single years between 12.1 and 22.9. British Sub-Aqua Club (BSAC) members had 14.4 per 100,000 over the same years. DAN Europe members, who include proportionally more dive professionals, were at about 20 per 100,000 in DAN's 2019 report; an earlier DAN analysis of 13 years of DAN Europe insurance data had put that group far higher, at 71. DAN's analysts point out that accident insurance may attract people who dive more often or more aggressively than the average diver.

A rate per diver also ignores how much each person dives. DAN's fatalities workshop called deaths per dive the better measure of exposure, and every per-dive figure in the table below is under 2 per 100,000 dives. The rest of this page covers where the deaths come from. Skills and planning articles are collected in our safety guides.

Is scuba diving more dangerous than driving or jogging?

Measured per person per year, the risk is in the same range. At DAN's 2010 fatalities workshop, the 16.4 per 100,000 rate for insured DAN members was set beside 13 per 100,000 for jogging and 16 per 100,000 for motor vehicle accidents. The workshop summary called the three comparable and placed all of them in the band where UK Health and Safety Executive criteria say a reduction is desirable.

The authors treat these comparisons as a rough indicator of safety only, because exposure differs so much between activities. They also found that death rates in occupational settings were often an order of magnitude lower.

Next to other water activities, diving ranks higher. A study of Australian coastal drowning deaths from mid-2004 to mid-2021 found that rock fishing and scuba diving had the highest drowning rates once participation was taken into account.

What causes most scuba diving deaths?

Drowning is the cause written on most death certificates, but it is usually the last link in a chain. A DAN study of 947 recreational open-circuit scuba deaths from 1992 to 2003 sorted each case into four steps: the trigger that started the trouble, the disabling agent that followed, the disabling injury, and the cause of death.

Read down the table and a common sequence appears. A diver runs short of gas, makes an emergency ascent and suffers an arterial gas embolism, where gas in the lungs expands during the ascent, typically with the breath held, ruptures the air sacs and sends bubbles into the arterial blood. The certificate may still say drowning. In the same study, 96% of embolism cases involved an emergency ascent and entrapment was present in 40% of asphyxia cases. The authors concluded that the disabling injury matters more than the recorded cause of death, because drowning is often secondary to it.

Later DAN reports point the same way. In the 2014 data, the most common known triggers were natural disease (18%) and running low on or out of air (9%), and DAN named cardiac events, insufficient gas and arterial gas embolism as the three leading modifiable causes. In 2019 a primary trigger could be identified in only 17 deaths, and loss of gas was the main one. DAN notes that root causes stay unknown in many cases because of missing information and inconclusive investigations.

How big a role do heart problems play?

A large one, and it grows with age. About a quarter of the deaths reviewed at DAN's 2010 workshop were associated with cardiac events, mostly in older divers. Among insured DAN members, death associated with a cardiac incident was 12.9 times more likely in divers aged 50 or older. In the 947-death review, cardiac incidents were linked to known cardiovascular disease (odds ratio 10.5) and to age over 40 (odds ratio 5.9).

Diving puts loads on the heart that daily life does not. The workshop summary describes how immersion and cold shift blood toward the centre of the body, which can lead to acute volume overload and heart failure, and how exertion raises blood pressure and can aggravate ischemia and arrhythmia. DAN's 2021 report adds the practical problem: a heart event that happens underwater carries a much higher risk than the same event on land, where drowning is not an issue and CPR can start without delay.

Autopsy data repeat the pattern. In DAN's 2014 data, high blood pressure and heart disease were the most common known pre-existing conditions, and 51% of those who died were obese, against 35% of the general population. A 2018 review of 122 deaths outside training in North America and the Caribbean found that 57% were associated with a medical event such as a heart attack, and the odds of a death being medical rose about 2.4 times for every 10 years of age.

Who is most at risk?

The research points to older divers, divers with heart or metabolic disease, and divers who step outside accepted practice. Experience on its own does not protect.

• Age. Among insured DAN members, the yearly fatality rate was 10 per 100,000 for divers up to age 25 and nearly 35 per 100,000 at age 65. In DAN's 2019 worldwide data, 44% of those who died were 50 or older.
• Sex. Men in their thirties had six times the risk of women the same age. The gap narrowed with age, and after 60 the rates were similar.
• Health. Hypertension, cardiovascular disease, obesity and diabetes recur in DAN's case data for 2014 and 2019.
• Experience. In DAN's 2020 data, experience level was recorded for only 21 deaths. Seventeen were divers with 61 or more logged dives, 13 of them over 50, and most were doing higher-risk diving such as cave, mine or rebreather dives or diving in adverse conditions.
• Breaking the rules of training. In the review of 122 deaths outside training, violations of accepted safe diving practice were found in 75% of the deaths without a medical cause. The odds of a non-medical death rose about 60% for each additional 10 m (33 ft) of depth.

How can you lower your risk?

Most of the risk sits in things a diver controls: health, gas, ascents and staying inside training limits. These steps come straight from the fatality research above.

• Get a medical check that looks at your heart. DAN's 2021 report recommends periodic medical examinations for men over 45 and women over 50, periodic evaluation for divers with several cardiovascular risk factors, and exercise tolerance testing before a diver with a diagnosed heart condition is cleared.
• Stay fit for the dives you do. The authors of the DAN member study advise older divers to keep fit with regular exercise and to avoid diving in conditions likely to demand physical effort they are not used to.
• Plan your gas, including the gas that two divers need to reach the surface together. The worked example below shows how much that is.
• Practise the skills that fail in accidents. The DAN workshop suggested skill refreshers with check-out dives, buoyancy control rehearsals, and gas management and alternate air source practice.
• Carry a cutting device, and stay out of overhead environments such as caves and wreck interiors unless you are trained for them. Both were workshop recommendations against entanglement and entrapment.
• Stay with your buddy and inside your training. The workshop listed buddy separation and dives beyond a diver's training, experience or physical capacity as suspected factors that still need firm evidence. The 122-death review adds hard numbers on rule-breaking.
• Know the emergency plan before you get wet. DAN advises calling local emergency services first in a life-threatening emergency, then the DAN Emergency Hotline on +1-919-684-9111, which is staffed 24 hours a day.

How much gas should you keep for an emergency?

Enough for two divers to deal with a problem at the deepest point and then ascend together on one tank. Our gas planning calculator calls this rock bottom. It assumes 1 minute of problem solving at maximum depth, an ascent to 5 m at 9 m/min, a 3-minute stop at 5 m, the last 5 m to the surface at the same rate, and two divers each breathing at a stressed rate.

Worked example: maximum depth 30 m (98 ft), a 12 L tank, and a stressed breathing rate of 40 L/min per diver, which is double a normal SAC of 20 L/min. The calculator returns 1,347 L. In a 12 L tank that is 115 bar after rounding up to the next 5 bar, and the ascent to the stop takes about 2.8 minutes. On a 200 bar fill, the ascent should begin by the time the gauge reads 115 bar, whatever the planned bottom time says. The same inputs at 18 m (60 ft) give 75 bar.

That reserve targets the most common trigger in the DAN review, where insufficient gas was the trigger in 41% of cases. If you don't know your own breathing rate, measure it first with the SAC calculator. Calculators are planning aids and do not replace training or a dive computer.