Nothing is more awesome or frightening than the concept of a 50-to-65-ton predator roaming our oceans. Megalodon, which fittingly means "big tooth" in Greek, is the name of a species of gargantuan shark that fossils indicate exceeded 50 ft. in length. But good news for beachgoers: scientists estimate that the megalodon has been extinct for well over 1 million years. Yet, this fact has not stopped some of Hollywood's greatest B-movie minds from resurrecting the beast for classic monster movies: Shark Attack 3: Megalodon, Mega Shark Versus Giant Octopus and Mega Shark Versus Crocosaurus.