Deep on the ocean floor, a mining operation discovers a sunken Russian shipped called Leviathan. One of the divers uncovers a safe--and when they bring it back to the base and open it there's just some records--and a bottle of vodka. A few people drink from it--and they become infected with what killed the Russian crew. It's a mutating virus, which transforms their bodies into this weird fish-monster--and it continues to absorb the crew, one by one. The man who runs the odd assortment of crew is Steven Beck (Peter Weller of STAR TREK: INTO DARKNESS) and he's at odds with the Doctor, who doesn't seem to have the crews best interest in mind.
This is very similar to the movie DEEPSTAR SIX, which was released the same year--but this is the better movie.