Have't seen this movie some 13 years

I always remembered that movie with the ending scene being somewhere betwee laguna riff and hard, rocky cliffs.

Then there is a shark or something just really confusing and dramatic is going on, I remember some person getting the really tense threatening.

As said: There is some sea-creature of sorts, but I didn't remember what actually is going on, whats the point of it all and what creature!
But I'm watching this movie again right now and I can't believe I found it again and I'm a 100% sure it's this movie. Sometimes you simply remember certain movies and their specific look there is no mistake.

This certain "ending scene" has so stuck with me that I still remember it to this day. Just not whats going on.
Since Robert Shaw is part of it and Jaws is my alltime favourite Am really happy this movie is awesome