However, some sharks, like the great white , can elevate their body temperature above that of their surroundings. Sharks don't blink. They have upper and lower eyelids, but these lids don't move and don't close over the eye. When biting prey, some sharks protect their eyes with a third eyelid called the nictitating membrane . Because most are cold-blooded, they don't have to eat as much as a human eats.
Some sharks can live for a year without eating, surviving on the oil stored in their livers.
The largest shark is the whale shark. At over 45 feet, it's also the world's largest fish. The whale shark strains out tiny animals that drift in the sea, such as plankton, shrimp, and small fish. The smallest shark is the spined pygmy shark. It's less than 10 inches long and can be found in the cold, deep oceans.