UFO (1970)

S1E8 Sub-Smash

Believing that a UFO might have caused a freighter to sink, Straker, Foster, and Nina Barry set out on an investigation aboard Skydiver. During their mission, they come under assault from an underwater UFO, leading to their submarine being stranded on a ledge at the ocean floor, leaving the crew trapped. As Straker battles his fear of confined spaces, Nina finds herself confronting a terrifying ordeal...