Megalodon prehistoric shark, artwork, hunting a school of fish. Megalodon, Carcharocles (Carcharodon) megalodon, lived between around 20 and 1.2 million years ago, and is known only from fossils. It was related to the modern great white shark, and possibly preyed mainly on whales. Megalodon was thought to attain lengths exceeding 20 metres, and possibly much larger. It is thought that it died out after the seas cooled, allowing warmblooded whales to escape the sharks for much of the year by swimming to waters too cold for them to survive in.