Shark Trouble by Peter Benchley

surface of the water, or silvery flashes as feeding fish roll out of the water and their scales catch the sunlight, or a patch of action anywhere in an otherwise calm sea, don’t go in the water. Nature’s food chain is in process, and there’s a chance that the apex predator that inhabits the very top of that chain is out hunting, too.
    Don’t go in the water if you’re bleeding—at all, from anything, anywhere on your body. The same salt water that may heal your cut or wound will carry away the scent of your blood. The sensory apparati of sharks are so finely tuned that they can receive and analyze the tiniest bits of blood imaginable and can direct the shark to home in on the source of the blood from far, far away.
    Blood is not the only attractant that emanates from us humans; we emit sounds, smells, pressure waves, and electromagnetic fields—all of which a shark can detect. That shouldn’t surprise you: you know that your dog or cat hears and sees in spectral ranges far beyond ours, so why shouldn’t a shark? After all, sharks have been around, and very successful, for scores of millions of years longer than cats, dogs, and people.
    Don’t swim or surf in water near seal or sea lion colonies. The playful and alluring pinnipeds are the prime (and favorite) food source for, among others, great white sharks. A surfer on a board appears, when seen from below, indistinguishable from a sea lion that has come up for a breath of air. Great whites are, by nature, ambushers; they prefer to blindside their prey, attacking from below and behind, and with such speed and force that they sometimes bite through surfer
and
surfboard before they realize they’ve made a mistake.
    Don’t go swimming at dawn, dusk, or night. Many sharks—tigers, for example—come into the shallows at night to feed. On some islands, locals swear that sharks can tell when six o’clock in the evening comes along, for that’s when fins can be seen crisscrossing the bay or cruising along the beach. Dim light, furthermore, decreases a shark’s vision, forcing it to rely on its other senses and thus increasing the chances of a random bite.
    The same holds true for swimming in turbid or murky water. A shark may sense nearby movement of a warm-blooded animal that it can’t see and may decide to bite as a test of edibility.
    Don’t swim alone, and don’t swim far from shore or other people. As a lone swimmer you are vulnerable prey—and the farther you are from rescue if something untoward does happen, the lower your chances of survival.
    Don’t go swimming where people are fishing from boats. They’ve probably put bait in the water, or even chum, which is a mixture of blood, oil, guts, and fish bits. (Even if you’re not set upon by a shark, you’ll stink for days, especially your hair.)
    Finally, and most obvious, don’t go swimming in areas where sharks are known to congregate or feed: steep drop-offs, where tide and current sweep prey to waiting sharks; the passes in tropical lagoons where, every six hours, the change of tide brings new feeding patterns to the entire chain of wildlife in the water; channels into harbors, where fish are cleaned and remains tossed overboard by returning boats.
    There are also a few don’ts for when you
do
go swimming.
    Don’t wear jewelry or any shiny metal in the water. It flashes and shines and can, in frothy or murky water, look to a shark like a wounded fish. A friend of mine went swimming wearing a bathing suit with a brass buckle. As he was wading out of chest-deep water, he felt something brush between his legs, and when he reached the beach he found that he’d been slashed open from thigh to knee—by something with extremely sharp teeth, either a barracuda or a small shark, for he never felt any pain. If there hadn’t been a lifeguard handy to put a tourniquet around his leg, he might have bled to