Whether it s a school report or simply a personal interest to be explored, Encarta opens the door to comprehensive information. Sharks are versatile and keen-sensed fishes, many species of which are able to hunt and eat nearly all the larger marine animals in both shallow and deep seas.
Sharks also reveal great diversity in behavior and size.
Sharks are chiefly marine fishes found in all seas and are especially abundant in tropical and subtropical waters. Many species migrate up rivers, however, and one, the bull shark, reaches Lake Nicaragua in Central America. Most sharks are gray in color and have leathery skin covered with small, sharp, pointed placoid scales, which, unlike those of bony fish, do not enlarge during the animal's growth. Usually five gill slits lie behind the head. The tail is asymmetrical, with the vertebral column extended into the upper lobe.