BULL SHARKS

The third shark that poses a true threat to humans in the sea is the bull shark. Bull sharks come in several varieties, including the Zambezi shark, the Lake Nicaragua shark, and several of the so-called whalers of Australia. As the first two names imply, bull sharks are even more wide-ranging than tigers. They have been found in—and have killed people in—lakes and rivers. Most sharks can't survive, not to mention hunt and feed, in brackish water. But bull sharks can function normally in salt, brackish, and fresh water.

Bull sharks are common in shallow water and murky water, like that off the Gulf Coast of Florida. It was a bull shark that attacked young Jesse Arbogast in July 2001, triggering the media frenzy that lasted all summer. And bull sharks were probably the culprits in the two nonfatal attacks a month later in the shallow waters off Grand Bahama Island. Bull sharks have such a bad reputation for being aggressive, fearless, and territorial that they undoubtedly are blamed for more attacks than they're responsible for. Still, there are so many bull sharks in so many waters in which so many people choose to swim that they must be classified as extremely dangerous.