Scientific name: superorder: selachimorphaSharks are a type of large fish that live in the sea. There are many different varieties of shark. Some eat smaller fish, some eat penguins and seals, and others eat the same way as large whales, by sifting out tiny sea animals from the water. Sharks constantly grow new teeth, and can lose thousands in their lifetime. Their skeleton is not made of bone, unlike most fish and animals, but is made from something softer and more flexible called cartilage. In people, cartilage is found around the ends of our bones to make our joints easier to move.