Fish, such as sharks, whose bones are composed of cartilage rather than hard bones, are called cartilaginous fish. There are about 700 species of cartilaginous fish, almost all of which are carnivores living in seawater. Cartilaginous fish have a streamlined body and paired fins. Their epidermis is covered with peltate scales and their texture is quite rough. Because they are streamlined, they swim very fast.