I just stumbled across this thread, and thought I’d post this to see if this rings a bell for anyone:

I remember seeing the end a movie sometime around the late 70s or early 80s (possibly made-for-TV) in which people were shooting at what I remember to be some kind of grey tar/sludge monster. I seem to remember this shootout happening on a ship, with the creature possibly at the top of a mast, but I can’t recall this part with certainty. I believe the monster is then shot/killed, and it seems like a happy ending is about to unfold, but I remember the last shot pans or zooms in on some sort of vat/drum full of the same grey, bubbling liquid that the monster was made of, which I guess was meant to insinuate the creature could return.

Sound familiar to anyone?