Understanding Risk

This is the first of four blogs that I’ve written about risk and risk management. This entry is a general introduction to the topic for anyone who’s thinking about taking their first scuba course. The other three entries are required reading for all my students: Equipment Risk, Equalization Risk and Buddy Risk.

PADI policy states that SAFETY is the #1 objective on every dive. To meet this safety objective, a diver must competently manage and balance a wide range of risks every moment of every dive.

Risk is defined as the negative consequences to a diver of some undesirable event happening to them. These consequences might be minor, or they might be very, very severe. The probability of any such undesirable event occurring might be knowable, or it might be uncertain and unpredictable. The choices and decisions you make from moment to moment will determine both the probability and the severity of negative consequences.

In my research for this lengthy blog, I've come across some useful concepts and statistics that will help to identify and quantify the variety of risks that you'll face as a novice scuba diver.  A competent, skilled diver will be aware of the major and minor knowable risks on every dive, will plan and execute their dives accordingly, and will be mentally prepared with contingency plans to balance and manage known risks actively throughout a dive.  Unknowable, uncertain and random risks must be dealt with as they occur.

Diving also exposes you to medical risks, which are influenced by your personal physiology and state of health.

Psychological and emotional factors can also have a major influence on a divers’ risk profile.  I've encountered risk-takers, risk-avoiders, thrill-seekers and the risk-oblivious. And I’ve had to rescue many panicked divers.

My goal here at VSds is to inform and guide clients to become proficient risk managers. To manage risks competently, a diver needs first to understand them.

Risk = The Cost of an Undesirable Event

Some of the risks in diving are insignificant in the grand scheme of things: losing or breaking some piece of equipment, a dive cut short in order to honour your commitment to the buddy system….minor inconveniences, spoiled dive days and financial costs.

On the other hand, some risks have seriously undesirable consequences that every new diver needs to be aware of and understand: the risk of sudden death and the risk of a serious injury causing long term disability. Consequences can be acute or chronic. Let’s honestly examine some relevant risk concepts and accident statistics, then draw some conclusions.

Measuring the risk of dying today

Have you ever heard of a micromort? It’s a unit of measurement, and it measures the risk/probability of dying today as you go about living your life. Everyone alive today is facing a baseline risk of 1 micromort. In simple terms, there’s a one-in-a-million chance that any individual will die today. It’s a very low probability, but it’s not zero. And the risks you take start to increase when you get out of bed in the morning.

Here’s how Wikipedia defines it:

Here's a link: https://en.wikipedia.org/wiki/Micromort


The wiki entry is fairly short and the stats are not current, but it contains some fascinating and (in)credible insights, comparing the risk of sudden death that we all face every day when participating in various activities. So let's have some fun with numbers.

Here is a short list of some activities that add 1 micromort to the baseline risk,  or approximately doubling the risk of dying today if you decide not to spend it in bed:

walking 27km

riding your bicycle 16km

driving your car 370km

traveling 1600km by jet

going skiing

taking 2 tablets of the drug ecstacy. (that's a wtf statistic!)

Now let's look at some extreme sports :

riding a motorcycle 50km: add 5 micromorts

running a marathon: add 7 micromorts

hang gliding: add 8 micromorts per flight

skydiving: add 8-9 micromorts per jump

And finally (drum roll), if you go on a two-tank dive, add 5-10 micromorts per dive, or 10-20 total micromorts per day, depending on your skill level. Novice divers and inadequately-trained divers are at the high end, facing 20 times the baseline risk of death.

We each have our own unique set of risk preferences. We pick our poisons, so to speak, depending partly on what exhilarates us or taps into our fears. Scuba diving offers plenty of both. So if you want to take up diving, you need to inform yourself and decide in advance on what quality and level of training you will need to keep yourself safe... as well as exhilarated.

How much would you pay to avoid a 1-in-a-million risk of dying today?

Now that we've quantified the relative risk of death by scuba, the question is... How much would you be willing to pay to avoid a 10-in-a-million (10 micromort) chance of death?

The wiki article argues that, generally speaking, when someone makes an initial decision to spend some dollar amount of money on their safety, they are very unlikely to spend significantly more money at a later date to further enhance that level of safety. People get comfortable, or complacent with their perception of risk. 

The implication for scuba diving is that a typical novice student who enrolls in a cheaply-priced group dive course, offering minimal safety training and skill development, is unlikely to invest later in higher levels of personal training and safety equipment. In other words, if someone is willing to spend a maximum of $500 on an entry-level group diving course, which subjects him or her to a 20 times increase in the baseline risk of injury or death every dive day, then he or she will probably not be willing to spend another $1,000 later for fuller training and safety equipment to cut that risk in half.

This is certainly true in the world of diving.  Almost nobody comes back for more training after the Open Water course.  And it's not because they don't need any more training. Most divers remain marginally-skilled or choose to drop the sport entirely rather than invest in the additional training that would raise their skills, confidence, safety and quality of experience. Fewer than 10% of all Open Water divers ever take an Advanced course. And an even tinier percentage of divers ever take a Rescue course.

In short, your initial personal and financial investment in diver training is probably all you will ever make. And this initial investment in training will essentially lock you into a lower or higher risk category that you'll not significantly improve on in future years.

Dive Accident Statistics

Introducing DAN

The authoritative source of data on dive injuries and fatalities in North America is Divers Alert Network, or DAN. https://www.diversalertnetwork.org. Their 2013, 2015, and 2017 reports were the sources for this blog entry. 

The data that DAN have collected are not complete. North American (US and Canadian) statistics are fairly extensive and detailed, while foreign and tropical dive incident statistics are more limited. Incidentally, in many parts of the world diving accidents are deliberately suppressed from public knowledge, for reasons including the protection of local tourist industries. So we don’t often hear about diving accidents, even though they happen every day.

It’s reasonable to assume that the North American dive industry (dive shops, professional instructors/divemasters and tour operators) adhere to higher standards of safety than in many tropical countries, for a variety of reasons including massive litigation risk and the enforcement of minimum safety standards by the industry’s leading training organization: PADI. But in 2nd and 3rd world countries, the safety risks that divers are exposed to are likely much higher. There’s no data to support that assertion, but personal experience tells me that this is true.

DAN stresses that their data should not be used to draw specific conclusions and inferences about the risks involved in diving or the frequency of accidents, but rather as a general indication of the types of injuries and fatalities that do get reported.

DAN’s dive injury and fatality statistics

Here are some notable statistics and factoids drawn from various sections of the DAN report.

DAN estimates that there are 3 million divers in the U.S., and that there are about 2 deaths per 100,000 divers per year, with 20 ER admissions per death and many more primary care visits. That's converts to 60 deaths, 1,200 ER admissions, and thousands of primary care visits every year for those 3 million divers.

In 2013, 68% of all reported dive incidents (fatal and non-fatal) involved a victim with less than 2 years experience from their date of certification.

64% of all reported deaths were during a pleasure dive, and 8% were during a training dive.

59% of incidents were on the first dive of the day.

When depth of dive was known, 25% of fatalities were in water less than 10m deep and 28% of fatalities were in water 10-18m deep. This means that more than half of fatalities occurred on shallow dives within the limits of a basic Open Water certification.

81% of fatalities involved circumstances that began to go wrong either at the deepest part of the dive (49%), during the ascent phase (9%) or at the surface after the dive (23%). Incidentally, a high percentage of victims found dead on the bottom still had their lead weights in position.

In 2013, 78% of male fatalities and 90% of female fatalities were over the age of 40. (2015- 91% of males and 93% of females were over 40; and 75% of males and 71% of females were over 50). It’s not the wild kids getting themselves killed scuba diving. According to PADI, the average age of novice scuba divers is in the late 30’s.

The medical histories of most victims were not available, but of those that were, 12% had a history of high blood pressure and 5% heart disease.

Body Mass Index (BMI) data were available for about half of all fatalities in 2013. Of these, 47% were overweight (BMI 25-29.9) and 35% were obese (BMI 30-39.9). In 2014, 51% of victims were obese and in 2015, 37% were obese.

Panic, running out of gas to breathe, and rapid ascent were the three most common mechanisms leading to injury and death, each at about 30-31% of the total. I've had personal experience with client panic, low or out of air situations, and ear injuries. Yes, they're pretty common.

The main causes of death were cardiovascular disease, drowning and arterial gas embolism. Interestingly, decompression sickness (ie. the bends) ranked very low, the 6th most common cause of death.  DCS doesn’t always kill, but was involved in 39% of reported non-fatal injuries, the most common of all non-fatal injuries. It can be a gruesome way to die.

Ear injuries were in second place, at 17% of the total reported injuries. 

Of all deaths where underwater visibility conditions were reported, 22% were in low viz (<3m) and 48% were in moderate viz (3-15m) environments, or 70% of the total. Unfortunately, this statistic isn’t very useful because the range of moderate viz is too broad. Three meter viz is a very different risk environment compared to 15m viz. In local Howe Sound waters, viz for most of the year is 7m or less. During the summertime the viz is often zero down to the bottom, and dive shops send large groups into this soup every weekend.

Equipment problems were frequently associated with dive incidents, with 25% of all reported incidents happening in conjunction with equipment failure. The most common equipment problems were with regulator free-flow and BCD (buoyancy control device) malfunction.

The local ocean environment itself presents sudden, unexpected risks. There are no seriously threatening animals in BC waters (except maybe sea lions), but there are stinging lions mane jellyfish, curious biting seals, and defensive ling cod mothers protecting their eggs. 

I've done a lot of tropical diving too, where the risks from aggressive or dangerous animals are much higher than in BC. And tourist dive guides don't necessarily explain all the knowable and random risks in their pre-dive briefings. In many countries the diving industry is essentially self-regulated, or faces little to no litigation risk.

All of these problems and dangers require competent risk management strategies and responses for a diver to remain safe.

Analysis and conclusions

It seems clear from the data that individual fitness, dive training and skills, equipment maintenance and prevailing diving conditions can and do explain differences in diving outcomes between safe diving and injury or death.

If you're thinking about taking your first scuba course, the dollar amount of your initial investment in training and equipment will largely determine the amount of risk (in micromorts) that you’ll be taking on as a certified scuba diver for the rest of your diving days. Competent divers face half the risk that a problem will turn into a fatality, compared to weak-skilled divers. When dealing with problems, well-trained divers are much more likely to take appropriate actions. On the other hand, bad decisions often lead to more bad decisions and to dive accidents.

Expressed in hypothetical micromorts, an unskilled novice diver who’s paid a rock bottom $500 price - for a typical large-group Open Water course with minimal training time and minimal direct instructor interaction - is 20 times more likely to die when diving today than if they spent the day in bed. And they’re much more likely to suffer a serious injury that could result in a long term physical impairment.

Would you pay an extra $1,000 for private personal diver training to cut that life-long risk of sudden death or serious injury in half?  99.9% of risk-oblivious novices just say no. 

Posted on January 26, 2016 .