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The head of a sand tiger sharkThe head of a sand tiger shark Sharks are a kind of cartilaginous fish: they have skeletons made of soft cartilage (gristle) rather than rigid bone. They live in all the world’s oceans. Sharks are mostly predators, although the largest kinds of all, including the whale shark and basking shark, feed only on krill or small fish. Sharks rely on their sense of smell and their ability to detect movement in the water to hunt their prey. They also have special sense organs that sense electrical currents made by the muscle movements of prey. Many sharks have large, razor-sharp teeth set in rows.

A shark's tooth-like scales in close-upA shark's tooth-like scales in close-up

Skin and bones

A shark’s skin feels like sandpaper to touch. It is covered by tiny, teeth-like scales called dermal denticles. Each scale is even made of dentine with an outer covering of enamel—just as teeth are. The covering makes the shark more streamlined in the water.

Sharks do not have any bones in their bodies. Instead, their skeletons are made of tough, flexible gristle or cartilage. Cartilage is much lighter than bone, significantly reducing the shark's weight and thus saving it energy when swimming.

About 50 to 70 shark attacks are reported every year. Of these, less than four attacks each year on average prove to be fatal.

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