Recently saw a frightful film on TV called "The Cabin by the Lake" starring Judd Nelson as the serial killer who abducts women, chucks them into a lake with a cinder block tied to their feet, and then makes an underwater "garden" out of them, diving there every day, to "tend" the garden, and occasionally change the victims' outfits....
Keralucu mentioned "Shark Attack" - don't forget "Shark Attack II" - sheesh! The budget version of the also crap "Deep Blue Sea" including super intelligent great whites, which GROWL like bears when closing in the for the kill, so the divers had some warning they were coming!. Painful.
Not a movie, but the BBC have just released a documentary series called "The Blue Planet" 400 mins plus of awesome u/w videography covering all aspects of the marine environment.
Final point - The Abyss - must be one of my most watched movies (both versions), but can someone please explain how Ed Harris and Co managed to exit the rig without being crushed to death? Serious flaw on James Cameron's part.