Dennis Hopper flirts with an evil mermaid?

"A young sailor falls in love with a mysterious woman, performing as a mermaid at the local carnival. He soon comes to suspect the girl might be a real mermaid, who draws men to a watery death during the full moon."

Movies on Youtube.

The trailer: https://www.youtube.com/watch?v=iZ6-ZcVzzIQ
https://www.imdb.com/title/tt0055230/reference