Villain(s)  Ocean cyborgs, mad scientist

Actor(s):  Sonny Chiba, Peggy Neal, Franz Gruber, Andrew Hughes

Brief Description  Terror Beneath the Sea (1966)—originally released in Japan as Kaitei Daisens? ("The Great Undersea War")—is a cult classic Japanese-American science fiction horror film directed by Hajime Sato and produced by Toei Company. Fusing elements of 1960s James Bond-style spy thrillers with classic rubber-suit creature features, the movie is best remembered for starring a young Shinichi "Sonny" Chiba in one of his earliest lead roles.

Plot:
Intrepid journalists Ken Abe (Sonny Chiba) and Jenny Gleason (Peggy Neal) are covering a U.S. Navy guided nuclear torpedo test in the Pacific. During the exercise, an unusual, humanoid creature swims past the naval vessel's underwater view screen. Dismissed by Navy officials, Ken and Jenny decide to go scuba diving near the site to find answers. Underwater, they are ambushed and captured by a group of strange, gill-bearing creatures. They wake up inside a high-tech, secret underwater city located thousands of miles below the ocean surface. The base is run by a megalomaniacal mad scientist, Dr. Moore, who has constructed the facility using nuclear power and waste.

Dr. Moore reveals that the creatures they saw are "Water Cyborgs"—unfortunate human beings captured from the surface and surgically transformed into mindless, metallic-silver amphibian servants. Dr. Moore plans to build an unstoppable army of these creatures to invade and conquer the surface world. Ken and Jenny are scheduled to undergo the agonizing cybernetic transformation process themselves. They must leverage their wits, engage in martial arts scuffles, and stage a desperate breakout before Dr. Moore's surgical team alters them forever, all while the U.S. Navy closes in to locate them.