Very few scenes involved stunt people. When Bud drags Lindsey back to the rig, that's really Mary Elizabeth Mastrantonio holding her breath. When the rig is being flooded and characters are running from water, drowning behind closed doors, and dodging exploding parts of the rig, those are all actors, not stunt people.
During the rigorous and problematic shoot, the cast and crew began calling the film by various derogatory names such as "Son Of Abyss", "The Abuse" and "Life's Abyss And Then You Dive". Director James Cameron said that he got so tired from working 6 days a week, 10 hours a day (sometimes more) that he would sometimes fall asleep during dinner in bed, waking up in the morning with a half-eaten plate on his chest and clenching a fork in his hand. Mary Elizabeth Mastrantonio reportedly suffered a physical and emotional breakdown because she was pushed so hard on the set, and Ed Harris had to pull over his car at one time while driving home, because he burst into spontaneous crying.
Ed Harris reportedly punched James Cameron in the face after he kept filming while he was nearly drowning.
Real oxygenated fluorocarbon fluid was used in the rat fluid breathing scene. Dr. Johannes Kylstra and Dr. Peter Bennett of Duke University pioneered this technique and consulted on the film, giving detailed instructions on how to prepare the fluid. The only reason for cutting to the actors' faces was to avoid showing the rats defecating from momentary panic as they began breathing the fluid.
The production was plagued by adversities and setbacks. There were engineering delays that slowed down production on the never-used nuclear reactor that served as the water tank as well as the sets within, and when the tank was finally filled, thunderstorms and pipe ruptures complicated things. The tank was so huge that it had its own weather, and the water was often too murky to film. Local goats sometimes invaded the set, destroying equipment and urinating over the floors. Delays caused shooting days to last an average of 15 to 18 hours near the end, which caused exhaustion and agitation among cast and crew, who already had a tough time dealing with James Cameron's relentless pace and dictatorial behavior. The constant cold and submersion caused many to come down with ear and sinus infections, there were many near-drowning accidents on set, and finally, filming was delayed one day due to a bomb threat.
James Cameron: [nukes] the movie plays at the height of the cold war, the nuclear threat is a theme running throughout the movie. There are also actual nuclear weapons seen in the movie.
James Cameron: [strong female lead] Lindsey Brigman (Mary Elizabeth Mastrantonio) is ambitious, combative and willing to make sacrifices.
James Cameron: [Biehn's hand] Michael Biehn's character gets bitten on the arm by another character - see The Terminator (1984) and Aliens (1986).
James Cameron: [title fade] at the beginning of the movie, the blue "Y" from the opening credits extends and then fades to the underwater scenery with the submarine.
James Cameron: [feet] when the soldiers arrive at the supply ship and jump out of the helicopters. See also Aliens (1986).