UFO - Season 1 - Eps 24: Reflections in the Water
A mysterious dome is found under the sea, that at first looks like the Moon crashed into the ocean. Inside the dome, they find duplicates of SHADO HQ personnel, using non-alien technology - cassette tape recorders - to imitate SHADO instructions to Moonbase and Skydiver.
About UFO

Title: UFO
First Air Date: 1970-09-16
Last Air Date: 1973-03-15
Status: Ended
Rating: 7.6/10 (from 45 votes)
Language: EN
Seasons: 2
Total Episodes: 26
Network: Associated Television
Genres: Sci-Fi & Fantasy, Drama, Action & Adventure
Production Companies: Century 21 Television, ITC Entertainment
Synopsis
A secret, high-technology international agency called SHADO defends Earth from alien invaders.
Cast

Ed Bishop
Cmdr. Ed Straker