Most fish can actually change colour to match the background. Some tropical fish can change almost instantly from yellow to scarlet or from red to green. Safe colours Some fish are brightly coloured or have striking markings, but most are camouflaged - that is, coloured to match their surroundings. Stingrays have broad fins that make them almost square, and a long, whip-like tail which can inflict a fearsome sting. They usually live in shallow tropical waters and feed on creatures on the sea-bed, such as shellfish and crabs.
Sharks are the most ferocious fish in the sea.
There are over 250 kinds, some quite small, but nearly all sharks are hunters, with a mouth full of rows of razor-sharp teeth. Fortunately, most prey on fish. Only 12 species are dangerous to humans. Most fish have skeletons of bone, but a shark's skeleton is made of a rubbery substance called cartilage, like the cartilage in your nose. Sharks also have gill slits on their heads rather than gill covers - typically five on each side.