Megalodon shark computer artwork A human swimmer is shown at top at the same scale This enormous shark Carcharodon megalodon lived between around and million years ago and is known from fossils It was related to the modern great white shark and is thought to have fed on whales as this is the only source of food that could have provided it with enough meat Megalodon was thought to attain lengths exceeding metres and possibly significantly larger It is thought that it died out after the seas cooled allowing warm blooded whales to escape the sharks for much of the year by swimming to waters too cold for them to survive in