Sharks are some of the calmest but most dangerous creatures on Earth. Some people think sharks are malicious, but according to the Florida Museum, the annual average number of shark attacks is only 63 incidents, which is a very small number. If a shark attacks you, you should not splash. If the shark comes towards you, you should push them away from you on their nose and most likely the shark will not come back. Sharks are saltwater fish, and their diet consists of seals, which are mammals. They also eat tuna and other large fish. A shark lives for about 80 to 130 years. Sharks extract DNA from their gills.