The Mermaids of Tiburon is a 1962 movie featuring several mermaids.
In 1964 the film was altered, cutting most of the mermaid footage, and adding some closeup shots of naked women swimming. In 1967, Most of the cut mermaid footage ended up being used in the TV series "Voyage to the Bottom of the Sea" season 3, episode 19, titled "The Mermaid". There, Diane Webber reprised her role as a mermaid using the same tail, and shot some extra scenes in a submarine. The same tail was also used in 1965, by Marta Kristen in Beach Blanket Bingo.
A diver is aided in his search for sunken treasure by beautiful mermaids.