The Abyss, 1989..
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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.
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.
Ed Harris reportedly punched
James Cameron in the face after he kept filming while he was nearly drowning.
James Cameron nearly drowned during production while he was weighed down at the bottom of the giant water tank during filming. His assistant director had failed to warn him to refill his oxygen, and realizing that he was running out of air, Cameron asked for help from underwater DP
Al Giddings. However, Giddings couldn't hear him (he was near-deaf from an old diving-bell accident), and with no one else nearby, Cameron realized he had to go top-side as soon as possible. He quickly released his helmet, harness and weights, and started to swim with great speed to the surface, exhaling all the way in order to prevent lung damage from decompression. One of the safety divers held him down and gave him a regulator, but it was broken and only produced water. Cameron tried to release himself, but the diver, thinking that Cameron was simply having a panic attack, held him even tighter. Cameron only survived because he punched the diver in the face, and reached the surface before passing out. The AD and the diver were fired the same day.