An originality-free Roger Corman movie which sets the plot of The Thing in the locale of Leviathan, but doesn't stretch the effects budget to much in the way of body-hopping alien parasites or deep-sea disaster.
An underwater mining team headed up by Alex (son of Wilfrid) Hyde-White and Melanie (daughter of William) Shatner discovers an alien parasite infiltrating the crew, prompting mad scientist Roddy McDowall to theorise at length about the life cycle of the "flying purple people eater from hell".
Occasional snappy lines ("What if it eats bullets like we eat after-dinner mints?") and a nicely cynical variation on the ending of The Thing are welcome, and it at least zips along at a fair old lick