The expedition departs for Atlantis, led by Commander Rourke (James Garner), who also led the search for the journal, and a team of specialists including Vinny (Don Novello), an Italian demolition expert, Audrey (Jacqueline Obradors), a Latino mechanic, Mrs. Packard (Florence Stanley), a grouchy radio operator, Dr. Sweet (Phil Morris), a black medical officer, and Cookie (Jim Varney), a mess cook. The crew sets off on the Ulysses, a giant submarine, but are soon attacked by the Leviathan, a robotic lobster-like sea monster, guarding the entrance to Atlantis. The Ulysses is destroyed, but Milo, Rourke and part of the crew escape and make their way to a cavern, which the journal describes as the entrance to the city.