Man from Atlantis - Season 1 - Eps 13: Deadly Carnival
Mark goes undercover to investigate members of a carnival planning to break into a museum. The only way to break into the museum is through an underwater tunnel, through which only Mark can swim. When he is approached, he refuses. The owner of the carnival is then kidnapped and threatened unless Mark helps.
About Man from Atlantis

Title: Man from Atlantis
First Air Date: 1977-09-22
Last Air Date: 1978-06-06
Status: Canceled
Rating: 6.4/10 (from 64 votes)
Language: EN
Seasons: 2
Total Episodes: 13
Network: NBC
Genres: Sci-Fi & Fantasy, Drama, Action & Adventure
Production Companies: Solow Production Company
Synopsis
Atlantis survivor Mark Harris breathes underwater, withstands extreme depth pressures and wields superhuman strength.
Cast

Patrick Duffy
Mark Harris

Belinda Montgomery
Dr. Elizabeth Merrill

Alan Fudge
Dr. Crawford

Jean Marie Hon
Jane