As you’ve probably guessed, “Underwater” is something of an assemblage of spare parts: “Alien” most obviously, though you’ll also hear echoes of “Event Horizon” and your choice of titles from the 1989 undersea horror derby (“Deep Star Six,” “Leviathan,” “Lords of the Deep,” etc.)
Think Leviathan (1989), DeepStar Six (1989), The Abyss (1989), and probably some films that didn’t come out in 1989 too.
1989 saw the release of THE ABYSS, DEEPSTAR SIX, and LEVIATHAN—with THE RIFT (aka ENDLESS DESCENT) coming out in 1990—and all featured an isolated crew in the unforgiving depths of the ocean encountering creatures and various personnel disasters.
Viewers expecting something along the lines of James Cameron’s The Abyss should probably recalibrate their expectations more along the lines of George P. Cosmatos’ 1989 thriller Leviathan .