Sharks are descended from the prehistoric Cladoselache fish from about 400 million years ago.

Not all sharks are dangerous - three out of 370 types are most often involved in attacks on humans: the great white shark, the tiger shark and the bull shark. Whitetip and blue shark have been known to bite victims of sea disasters.

Sharks have no bones - their internal supports are made of cartilage.

Slideshow: Oregon Coast Aquarium sharks

Sharks can detect electricity - the sixth sense lets them find stingrays hidden beneath the sand. They can also use the electrical sense to determine directions.

A shark is always teething and new ones don’t replace the old, they just grow back in. Sharks might lose between 12,000 and 30,000 teeth during its lifetime.

Some sharks lay eggs - some small sharks that live near the seafloor. Empty eggs of sharks, skates and rays often wash up on beaches and are called mermaid’s purses. Most sharks give birth to live young.

- Compiled from the Shark File Website

Attacks on humans are rare - according to the Florida Museum of Natural History's International Shark Attack File, there were 61 unprovoked shark attacks worldwide in 2004, resulting in seven deaths. More people die from lightning strikes.

Great whites prefer eating baby seals, they stalk seal colonies waiting for the animals. - from SaveOurSeas