Shark attacks wouldn’t seem so improbable if we knew more about their risk factors

Suppose you were planning to take a sightseeing stroll, one night, through the Miami neighborhood known as Little Havana, and you asked me, “Is it safe?”   And I replied, “Oh it’s very safe!  The overall rate of violent crime incidents in the US is only about 400 per 100,000 people per year, so your chances of getting mugged, maimed or killed on any one night in the US are only about 1 in 100,000.”

If I were to say such a thing, I’d be guilty of misusing statistics, wouldn’t I?  Because the risk of violent crime isn’t evenly distributed throughout the country.  It’s much higher in some places and at some times, such as in Little Havana at night.

And I think everybody pretty much gets that.  But somehow when it comes to shark attacks, we don’t get that.  At any given beach, at any given time, we are likely to cite the same broad statistics – or simply to shrug and assume that the chance of getting bitten by a shark is vanishingly small, like the chance of getting struck by lightning or winning the state lottery.

But here’s a discomfiting fact:  The risk of shark attack actually reaches 100% for people who are about to get attacked.  They just don’t know it.  They don’t know that they are swimming out too far, where the sharks and their fish-prey normally swim.  They don’t know that the temperature and the fish migration season mean that lots of sharks are in the area.  They don’t know it’s feeding time.  They don’t know that by peeing in their bathing suit they have gotten the sharks’ attention.  They don’t know that by being alone and making splashes at the surface, they embolden a shark to attack.

But wait, you say, don’t most shark attacks occur in knee-deep water?

Actually, no.  There is an informative website that apparently lists all reported shark attacks in recent history.  I went through the last 100 attacks, which covers roughly the last 54 weeks, and found that only 14 of these incidents seem to have happened in shallow water – that is, happened to people who were surf fishing, wading, standing, playing football (yes, at a beach on Isle of Palms, SC), body surfing or boogie boarding (on the East Coast, where the waves usually break near the beach), and did not involve shark aquariums or shark fishing.  Sharks can and sometimes do swim into depths so shallow that they nearly run aground, but it appears that the vast majority of their attacks on humans occur in relatively deep water, particularly to swimmers, surfers, scuba divers and spear-fishermen.

Admittedly, only about 100 reported attacks in a year is a small number.  But we shouldn’t divide that number by all the world’s swimmers, surfers, scuba divers, et al to get a rough idea of the overall risk.  Instead we should be mapping attacks (using those millions of dollars we lavish on marine biologists annually) at particular locations, times of day and times of year, water depths and swimmer activities – and yes, the risk will still seem small overall, but for certain times and places and water depths and swimmer activities, I think we will see telltale spikes in risk.  And we will know that there are certain places we shouldn’t go, certain things we shouldn’t do, if we want to keep the risk of being torn to pieces by a shark down to a level we can forget about.

Even now, I think that some high-shark-risk behaviors are pretty obvious, yet some people do them all the time.  Didn’t everybody see Jaws?

SARASOTA, Florida — An American student has described the moment she was bitten by a shark in an attack that almost punctured her lungs and left her needing more than 100 stitches.

Andrea Lynch, 20, said she was lucky to be alive after being attacked as she enjoyed a late-night swim with friends during a boat trip off Sarasota Bay in Florida.

As she floated on her back, the shark, believed to be a 7ft-long bull shark, sank its razor-sharp teeth into her side until they hit her ribs and pelvis.

It shook her briefly before letting go.


“I reached back with my hand and felt all these gashes on me, and there was blood running down my body and pooling in the boat,” she added.

The shark attack was reported to be the second near Sarasota Bay this year … [T]he potential severity of any shark attack – even by smaller sharks like the bull – was underlined when doctors said that Ms Lynch’s lungs were very nearly bitten through in the attack.