Leviathan (1989)

Hired by Martin (Meg Foster), the head of a major corporation, a crew including geologist Steven Beck (Peter Weller) descends to the ocean's depths for a mining project. When the undersea explorers find a sunken ship and investigate, they inadvertently bring a malevolent life form on board their vessel. The creature kills some crew members and causes them to mutate, resulting in a battle for survival against an unknown force far below the surface of the ocean.