Sharks have diversified into over 470 species. They range in size from the small dwarf lantern shark, a deep sea species of only 17 centimetres in length, to the whale shark, the largest fish in the world, which reaches approximately 12 metres. Sharks are found in all seas and do not live in freshwater except the bull shark and the river shark, which can survive in both seawater and freshwater. They breathe through five to seven gill slits. The great white shark, tiger shark, blue shark, mako shark, and the hammerhead shark are apex predators—creatures at the top of their underwater food chain.