There are over 300 species of sharks. Sharks have long torpedo-shaped bodies and skeletons made of cartilage, not bone.
Cartilage is very flexible.
You have cartilage in your ears and nose. The shark's skin is covered with teeth-like scales called dermal denticles. Dermal denticles cut down on drag when the shark is swimming. They also protect the shark from injury. Bony fish have gas-filled swim bladders that keep them afloat.