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Barracuda (1978)
(feddit.nl)
YOU CAN ALMOST HEAR THE SCREAMS! AS THE WATER BELOW BECOMES A CHURNING DEATHBED OF FLASHING TEARING TEETH!
A top secret government experiment leads to fatal barracuda attacks on the beaches of a small coastal town formerly renowned for its lobster. A marine biologist and a sheriff uncover a plot involving a former war-medic pioneering research into hypoglycemia and its effects on human behavior.
This one and Tentacles from Italy were the b-movie heavy hitters post-Jaws.
There was also The Deep, Orca and, from Mexico, Tintorera!, although that last one also had a bit of a softcore vibe to it, if I remember the rumors correctly, as I didn't see it.
¡Tintorera! is definitely a movie with a bit more sleaze, especially if you watch the longer cut.