Network: NBC
Episodes: 13 (hour)
Seasons: One

TV show dates: September 22, 1977 — June 6, 1978
Series status: Cancelled

Performers include: Patrick Duffy, Belinda Montgomery, Alan Fudge, Victor Buono, Robert Lussier, Richard Laurance Williams, J. Victor Lopez, Jean Marie Hon, and Anson Downes.

TV show description:
After a violent storm, a nearly-naked man (Patrick Duffy) is found washed up on a California beach near the Naval Undersea Center. He’s taken to a local hospital but they don’t know how to help him — he has webbed fingers and is dying.

Ultimately, a Navy doctor named Elizabeth Merrill (Belinda Montgomery) realizes that he can breathe underwater and saves his life. He appears to have amnesia and she takes him back to her lab for testing, naming him “Mark Harris.” They come to believe that he’s the last survivor of the underwater civilization of Atlantis. Along with his webbed feet, Mark has gills instead of lungs, can swim faster than dolphins, has superhuman strength, and can dive to incredible depths.

Mark helps the Navy to find a missing submarine that’s carrying top military officials and to foil the plans of insane genius Mr. Schubert (Victor Buono) to start World War III. Afterward, he’s free to return to the sea but decides to stay with Elizabeth. They work together as part of the Foundation For Oceanic Research, a governmental agency that conducts top secret research and end up facing extraterrestrial life and evil scientists as well.

They work under budget-conscious foundation director C. W. Crawford Jr. (Alan Fudge) and explore the depths of the ocean in a sophisticated submarine called the Cetacean. The crew of the Cetacean includes Jomo (Richard Laurance Williams), Chuey (J. Victor Lopez), Jane (Jean Marie Hon), and Allen (Anson Downes).

The series began as four successful TV movies that all aired in the spring of 1977. NBC then ordered a series, changed some of the elements, and the show only last 13 episodes.