A bit obscure but if you like science fiction you definitely should find this. Something is disrupting subs from their polar routes so the Government sends the Tiger Shark to find and destroy the threat. The usual grouping of military and scientists try to coexist in the cramp sub as they hunt down this unknown threat.
The beginning is done competently but it is standard early sci fi boiler plate. Once they get down to hunting the flying saucer though things pick up quite nicely. There are nice special effects and very good pacing. Plus a fun one eyed alien. Certainly it's the best finding aliens underwater film until "The Abyss."
Oh fun drinking game. Take a drink of your favorite beverage every time someone says "Atomic."