Seastalker (1984)

There's something down there in the ocean, something terrifying. And you have to face it -- because only you can save the Aquadome, the world's first undersea research station. The alarm sounds and your submarine, the Scimitar, is docked nearby. But not so fast -- you haven't even tested the Scimitar in deep water, and the crew at the Aquadome may have a traitor in its ranks. So be careful! You…