But if you do not feel like diving through the air, diving underwater provides more buoyancy, but has a different set of hazards. Jacques Cousteau turned scuba diving into a leisure activity with his development of the “Aqua-Lung” in 1943, and the British Sub-Aqua Club (BSAC) now has over 35,000 members. The BSAC keeps a careful tally of diving fatalities and recorded 197 deaths over the 12 years from 1998 to 2009, an average of around 16 a year. They estimated around 30 million dives over this time, so the average lethal risk was around 8 micromorts per dive: but this is an average – for BSAC members it was 5 per dive, 10 for non-members.
But what about something that you may think is less risky? Long-distance running might seem out of place in this list. But, as Pheidippides found 2,500 years ago after collapsing and dying from his 26-mile run to announce the victory at the Battle of Marathon, this event can end in more than sore feet. In 3.3 million marathon attempts in the US between 1975 and 2004 there were 26 sudden deaths, which comes out at around 7 micromorts a marathon on average – putting it at a similar level to a scuba-dive or a sky-dive.
When we look at sky-diving, scuba-diving, marathon running and other extreme sports, there seems to be some natural level of risk – say around 10 micromorts per episode – that people are prepared to take on for a challenging and exciting leisure activity, while still being reasonably sensible (this does not include BASE jumpers).
What is 10 micromorts equivalent to in regular life? Well, it is about the risk of death, from any cause at all, of an average 30-year-old man in 4 days of their normal life, or about 1 day for a 50-year-old. It is also roughly equivalent to the risk in the UK of a 60-mile (96km) motorbike ride, or 2,500 miles (4,000km) in a car, or having a general anaesthetic. Not that one can consider having a general anaesthetic as being a particularly enviable leisure activity.
Anyway, if there are further contributions to this column, you will know that I survived the sky-dive and lived to face another day. Wish me luck!