Scientists say sharks have lived in the world's oceans for millions of years, and there are more than 350 different kinds of sharks.

Sharks do not have bones, and a shark has an extremely good sense of smell.

It can find small amounts of substances in the water, such as blood, body liquids and chemicals produced by animals.

Sharks also sense electrical and magnetic power linked to nerves and muscles of living animals.

These powerful senses help to find their food.

Some sharks will eat just about anything.

Many unusual things have been found in the stomachs of some tiger sharks.

They include shoes, dogs, a cow's foot and metal protective clothing.