Ocean Watch

Since A shark tour group attracted that great white shark off Haleiwa a couple of weeks ago, people have been e-mailing and talking to me about sharks [see last week's Ocean Watch column, "Meeting with great white a great thrill"].

One woman told me, "After seeing 'Jaws' I never put a foot in the water again." I hear this often and am always astonished. How, I wonder, can a 31-year-old horror movie cause so many people to make such a big decision?

At the other extreme are people who not only put their feet in the water with sharks, they lay hands on their skin. Clients watched the great white from a cage, but the leader got out and swam with the big fish, touching it several times.

Do I think petting a great white shark is dangerous? people want to know. Yes, I say. And I wonder, What makes an experienced diver get out of a cage and touch a 17-foot great white?

Researchers in the science of risk management also have questions about how people judge risks and make decisions, and studies in this field have produced some theories. The simplest is survival. Our brains are wired to fear first, think later.

A portion of the brain called the thalamus reacts immediately to threats by releasing emergency hormones that cause us to run or fight. Thinking comes afterward with a slower part of the brain, the cerebral cortex.

Too much thinking, though, can be dangerous. A Harvard risk analyst found that some people decide what kind of lifestyle they want and then make up reasons to justify the risks that go with it.

Take commuting by bicycle. Those who like it say it is cheaper than driving, good for the environment, relatively safe if wearing a helmet and provides much-needed exercise.

Traveling a mile by bicycle, however, is 14 times as likely to be fatal than traveling a mile by car. Because the cyclist wants to ride, he believes he is much more in control than he really is.

Now we're getting somewhere. People who claim to stay out of the water for fear of sharks probably didn't like the ocean in the first place. Like the cyclists, they chose a lifestyle, terrestrial in this case, and then used "Jaws" to warrant it.

The shark lover is like the cyclists, too. He really, really wanted to swim with that shark, and defended doing so by noting the shark was calm, and therefore, believed a close encounter would be safe. Fulfilling the dream was apparently worth the risk.

Another reason fear of sharks is so widespread, risk analysts say, is because of the media coverage that results from an incident. When people hear about an attack over and over, it's easy to jump to the conclusion that sharks are knocking people off left and right.

They are not. An average of 33 people get bitten each year in U.S. waters out of about 2 billion beachgoers.

Deciding which risks to take in the ocean, or anywhere, is complicated and personal. But don't take it too seriously. "The ultimate risk is life," risk analysts joke, "and that has a 100 percent chance of leading to death."