Unlike most species of sharks, the nurse shark can pump water over its gills. Therefore, it does not have to swim constantly and often lies motionless on the sea bottom. Nurse sharks eat bottom-dwelling fish, crabs, lobsters, and shrimp. They have attacked people. But most of these attacks were caused by the victim, who foolishly grabbed a motionless nurse shark by the tail.
Thresher sharks are long-tailed subtropical fish that swim along the surface.
No thresher shark has been known to attack a person. Whale sharks, in spite of their enormous size, eat only plankton and small fish. Therefore, they are harmless to people. Whale sharks live in tropical waters. White sharks rank among the most dangerous sharks.