Fish are aquatic vertebrates, have fins, gills and cold blood, with few exceptions. Whale shark is the biggest fish, but whales and dolphins are mammals, they live in the sea but feed their babies with milk. Fish instead lay eggs.
Sharks: are very popular fish and they are believed to be one of the most ancient aquatic creatures. They have huge and powerful jaws with sharp teeth. They are mostly carnivores but some sharks are harmless and eat plankton. Sharks are hunted for food in many countries and some of them, like the Great White Shark, can attack people.