A futuristic underwater sea-lab is having problems with a UFO that's parked between them and a nearby deep ocean trench. As they investigate, they attract the unwanted attention of a dangerous creature who puts the scientists and crew in danger.
When some deep sea researchers feel their base being buzzed by a strange object, they assume it's a whale or some other natural occurrence Thing is, soon they realise that is a metallic object - like an aluminium sting-ray - and it contains extraterrestrial life that isn't that friendly. Now they are besieged and hundreds of feet under the surface with limited oxygen and a menacing foe. Can they escape? Well that's down to team leader "Wayne" (Scott Brady) who has, typically, to run a dysfunctional team of military and scientific brains who have baggage, of course, and seem to prefer fighting each other rather than their common foe. There's a lot of waffly dialogue and the orchestrations are left to create much of the menace as we are introduced to a nimble creature that as the film rumbled along I began to think could be dragooned into doing us all a bit of a service should it succeed on it's mission. It's good to see that that costume is getting put to good use, though - I'm sure I've seen it before, and those plastic chains.