The big kahuna of the fish world is the whale shark (Rhincodon typus), which lives in semi-tropical and warm temperate waters around the world and grows to more than 65 feet, weighing nearly 40 tons. With its tremendous length, gigantic blunt head and polka-dot pattern, the whale shark looks like the prototype for Roy Scheider's worst nightmare. In reality, the big fellas are pretty much harmless. They're so docile, in fact, that they've been known to allow swimmers to hitch rides on their backs. They're filter eaters, rather than biters, and feed on a diet of tiny plankton, small fishes, crustaceans and squid. They live to the age of about 70, unless humans harpoon them and grind them up into fish meal.