Terror of Mechagodzilla

Interpol agents search for the pieces of Mechagodzilla at the bottom of the Okinawan Sea. They use the submarine, Akatsuki, to gather information on the robot's builders, the alien Simeons. The Akatsuki is suddenly attacked by a giant aquatic dinosaur called Titanosaurus and the crew vanishes. With the help of marine biologist Akira Ichinose, they trace Titanosaurus to a reclusive, mad scientist named Shinzô Mafune.