Identify this horror movie?

Cafe Society
1

When I was a kid I saw this horror or “thriller/suspense” movie on TV. It was probably originally a theatrical release but I couldn’t swear to it. Likely late '70s, but could be a little earlier or later.

The main things I recall are that it was set on a ship that was out conducting oil/gas exploration or drilling. They “found something” buried deep below in the muck. Somehow it got on board? Or possessed people on board?

A scientist on the ship came up with the theory that it was some sort of ancient god related to sea lampreys. ??? I know it sounds whack and I might be way off, but that’s what I seem to recall as a kid.

2

Leviathan (1989)???

3

No. It was way earlier than that. I was in college in 1989, and I saw this movie as a kid. I’d say 1980 at the latest.

I’m thinking the title was something like “The Enemy Below” or something about “creature” and “depths” but I searched all sorts of permutations on IMDb and came up blank.

4

Maybe Warlords of the Deep (1978)?

5

There was a 1975 made-for-TV movie called Satan’s Triangle that had a plot somewhat similar to what you’re describing.

6

The Intruder Within?

7

That’s it!

Woo-hoo!

1981, made-for-TV, so I was a bit off, but that’s definitely the movie I was thinking of.