is this the movie ?
looking to match a couple of scenes with some titles. one scene is where someone diving reaches under a ledge and is grabbed by the arm by something and slammed repeatedly into a rock wall.
second scene which is likely from a different film altogether but had a similar aquatic horror/adventure theme. one or two people, perhaps children are walking down a beach and they turn over a piece of wreckage or wood or something and beneath it find an injured screaming person who is grossly humanoid or just covered in wounds and blood i cannot remember.
vague i know but have it fellow movie hounds. i pride myself on remembering scenes or sequences for other people but these two in particular have me at a loss.