What is this movie with multiple humanoid sea monsters?

(On behalf of someone else)

I saw a colorized (I think it was colorized, it has been a very long time, sorry) movie on T.V. many years back (60's - 80's movie approx), and I just cannot put a name to it, but all I remember is a fiery monster at a dock.

The monster looked like a combination between some sort of aquatic creature and a human (it is not "Octaman"), but I might be way off. Anyway, all I remember is if I remember correctly, two monsters clashed with each other at a dock, or the monster tried to commit suicide by using its arms to choke itself.

However, there were other beasts too, which I think lurked beneath the monster, so I think the monster was potentially clashing with another. One looked like a cat, and the other maybe a shark. I also remember someone putting the monster in a net, or either tried to put in some sort of device to put it back on the dock.

There were also piles of papers, or what looked like paper, surfaced on on top of the water.

Additionally, the monster has a Frankenstein monster shaped head, King Kong like nostrils, one or maybe three big exposing teeth, and a fish-like mouth; it also had smoke coming out of its nostrils, I think.

Now, I cannot remember much else of the movie, unfortunately, but I think the part was very dark until light shined though exposing the monster, and I cannot remember if the monster was inside or outside, but I have a sneaking suspicion it was outside.