The Rift

An experimental submarine, the "Siren II", with an experienced crew is sent to find out what happened to the missing "Siren I". They trace the Siren I's black box to an underwater rift; as they move in to retrieve it they encounter a dangerous seaweed-like fungus. Later they surface in a cave system where they discover that the company they are working for has been engaged in illegal genetic engineering experiments that have produced a variety of mutant creatures.