As an aside with the rat scene ... that wasn't special effects (though did have cuts). https://filmschoolrejects.com/the-abyss-breathing-fluid/ https://filmsch

As an aside with the rat scene ... that wasn't special effects (though did have cuts). https://filmschoolrejects.com/the-abyss-breathing-fluid/ https://filmschoolrejects.com/the-abyss-breathing-fluid/ > The rat demonstration scene in The Abyss was unsimulated and used real-life oxygenated breathing fluid. Ed Harris, however, was tasked with pretending to breathe in his water-filled helmet. This was especially challenging during underwater shots, of which there were many. > ... > Supposedly, the only purpose for the cuts in the sequence was to avoid showing the rats defecating from panic. In total, the crew shot the scene five times with five different rats. Aftercare included holding the rats upside down to drain their lungs of fluid coupled with a vet visit. None of these efforts assuaged the concerns of the English censors, who cut the scene for UK distribution. https://www.imdb.com/title/tt0096754/trivia/?item=tr0738209 https://www.imdb.com/title/tt0096754/trivia/?item=tr0738209 > Fluid breathing is a reality. Five rats were used for five different takes, all of whom survived and were given antibiotic shots by a vet. The rat that actually appeared in the film died of natural causes a few weeks before the film opened. According to James Cameron, the scene with the rat had to be edited out of the UK movie version because "the Royal Veterinarian felt that it was painful for the rat". James Cameron repeatedly assures that the rats used for this take didn't suffer any harm. --- Note that in https://en.wikipedia.org/wiki/Liquid_breathing https://en.wikipedia.org/wiki/Liquid_breathing the "Diving" section is under proposed uses. The human uses have been very limited to specific medical situations.