Sharks seem to be almost insensitive to pain, but this does not mean that they lack highly developed senses. Their sense of smell is so delicate that they are nicknamed the "swimming nose"; they can detect blood or a dying fish hundreds of yards away in the water. Experts had long thought that sharks' eyesight is poor and that they do not depend on it. But when an investigator put blinders on captive sharks at the Lerner Marine Laboratory in the Bahamas, they demonstrated their reliance on the visual sense by crashing head-on again and again into walls before learning to navigate by using their fins to feel their way.
The shark has very unusual teeth. Its mouth is literally studded with several sets of needle-sharp teeth, one row in back of another. These are loosely set in the jaw, and when the front ones break off or wear out, the spare teeth work their way forward to replace them. Shark bites have an unmistakable crescent shape and are often so deep that a major artery is severed. Many victims die from loss of blood before they can be taken to the shore.
Sharks will swallow anything: sea turtles, sea lions, birds, fish, cans, lobsters, horseshoe crabs, garbage, coal, people. One shark captured off an Australian dock had in its stomach half a ham, several legs of mutton, the hindquarters of a pig, the head and forelegs of a bulldog with a rope tied around its neck, a quantity of horseflesh, a piece of cloth and a ship's scraper. Another caught in the Adriatic, had an even stranger bellyful: three overcoats, a nylon raincoat and an automobile license plate.
