Leviathan

Beneath the waves lies an underwater mining base, home to 8 people who search for materials to bring up to the surface. On one of their missions under the sea, they discover a sunken Soviet submarine where everything suggests genetic experiments were being carried out, which supposedly gave rise to a monstrous, nearly indestructible creature. But the trouble doesn't end there, because those crew members directly exposed to the faulty results of this experiment begin to undergo a change that will turn them half-fish. The fight to escape the place and destroy the monster will determine their immediate fate, because otherwise they will be devoured by it.