But most types of sharks do not attack people.There are more than three hundred and fifty different varieties of sharks.Strangely enough,the most harmless sharks are usually the largest!
The basking shark,the whale shark,the hammered shark,the goblin shark and the megamouth sharks are all harmless.Only about four sharks are very dangerous to humans.They are the great white shark,the tiger shark,the bull shark and white-tip reef shark.The largest known shark lived more than 16 million years ago but is now extinct .It is called the Megalodon shark.It was more than twenty meters in length .The largest shark around today is the whale shark,which is whale shark,which is about twelve meters in length .Sharks have been around for about 400 million years.That means there were sharks in the oceans long before dinosaurs walked on the earth!Sharks are such good survivors that they have changed very little in the last 120 million years.Sharks eat fish, seals and other sea animals .They find their food by sight ,sound and smell .Sharks, like cats,have very good eyesight.They can hunt easily in clear or murky(dark and dirty)water.They can also hear very well in the water and they can smell food hundreds of meters away.
There are only about seventy-five shark attacks in the world each year.And only about ten people are killed by sharks .But each year,people kill millions of sharks because shark meat is considered a delicacy(a dish that everybody enjoys but is generally very expensive) in some countries.