I've been trying to find a movie that I remember as a child. It was about a group of people that were hunting giant sea creatures and there is this scene where they fire this harpoon through a piece of steel and it is a huge barbed thing. There is also this ghost of a woman, she may have been a woman who drowned and became a mermaid who seems to be in communication with a giant sea turtle. The lead character name is 'Marcus' or 'Magnus'. Has anyone seen this film? I saw it on TV late a night a couple of times. I've been searching IMDB without much success.

I've been trying to find a movie that I remember as a child. It was about a group of people that were hunting giant sea creatures and there is this scene where they fire this harpoon through a piece of steel and it is a huge barbed thing. There is also this ghost of a woman, she may have been a woman who drowned and became a mermaid who seems to be in communication with a giant sea turtle. The lead character name is 'Marcus' or 'Magnus'. Has anyone seen this film? I saw it on TV late a night a couple of times. I've been searching IMDB without much success.
The Bermuda Depths (1978)

The Bermuda Depths (1978)

Ive got that movie on disc