The Abyss, an underwater movie about petroleum engineers working with a navy SEAL to locate a submarine sunk under mysterious circumstances. They discover alien life living in our oceans but not in the Doctor Who, humans with funny heads mode. Quite unexpected and fascinating.
There's an amazing scene where the female lead has no alternative but to drown and then hope they can revive her, tense. Twists and turns, who's working for who, what's really going on, good stuff.