Leviathan

The Leviathan is a giant Atlantean artifact that was left near the underwater entrance to Atlantis so that it could protect the city from intruders. Being longer than a submarine, the Leviathan is a mechanical monstrosity that closely resembles a lobster. According to Milo Thatch, the Leviathan's lair has ships from every era, meaning that the giant has killed many men throughout the centuries. It is also capable of flight as seen just before the destruction of Atlantis.