Corrected entry: Several times in the film it is mentioned that the rig is on the ocean floor some seventeen hundred feet below the surface. Yet Lindsy swims without any protection from the wrecked submersible to the rig, and Bud and others swim from one module to another. The absolute maximum depth the unprotected human body can stand is less than six hundred feet, and that is in the case of superfit divers who spend years training for their record dives (and some die trying). At seventeen hundred feet the water pressure would crush an unprotected human being like a schnitzel.
Correction: For a moon pool to work, the pressure inside of the underwater habitat the pressure inside would have to be equal to the water pressure outside. 1700' would be 518 meters underwater, with a air pressure of nearly 53 times that of the surface. FYI The deepest scuba dive to date was 332.35 m. With scuba divers, you start to be at risk of oxygen toxicity at 6-7 atmospheres and symptoms increasing the longer the exposure. So the grew of the underwater habitat would have all died from oxygen toxicity pretty quickly, let alone the effect of nitrogen at 53 atmospheres on the body.
You're right that compressing normal atmosphere like that would cause problems with oxygen and nitrogen, but they're not breathing highly compressed normal air. When you go that deep, you breathe a special mix that has a much lower percentage of oxygen and nitrogen. Typically, helium is added since it is inert. Look up heliox and triox.
If they were all breathing the oxygen/helium mix used by deep-sea divers, they would all be talking like Mickey Mouse, and they aren't. Obviously, the filmmakers wanted to avoid this comical side effect of breathing in helium, but it still reinforces this mistake.
Corrected entry: The whole scene with the rat and the breathing fluid could never have happened because rats can't vomit, so the poor thing would have died.
Correction: Vomiting is the forceful ejection of stomach contents. It has nothing to do with ejecting substances from the lungs. That would be coughing, which rats *can* do.
Furthermore, that scene was NOT simulated. That was an actual rat breathing the actual oxygenated fluorocarbon fluid. It wasn't sci-fi; the concept exists, even if it hasn't seen much wide-scale testing on humans.
Other mistake: Near the beginning there is a scene where they are launching a submersible with Lindsey and the seal team in it. Lindsey waits until the sub is dangling over the water then pulls a lever and the sub drops about 10 feet into the water with a big splash. Several problems: 1) Those subs are hugely expensive. They put them in the water very gently. 2) Those subs are so expensive that they don't risk having a release mechanism as depicted. They use a standard screw shackle to ring and would have to have a swimmer let them go. 3) Due to the buoyancy of the sub, falling that far to the water would give all passengers back injuries due to the sudden deceleration when the sub hits the water.
Suggested correction: They're on an emergency rescue mission and don't have time to be delicate with the equipment. Also, everyone in the sub is shown being thrown around when the sub hits the water. Hence the angry looks toward Lindsey.
They would still put the sub safely in the water. The first thing in priority in a rescue situation is scene and crew safety. If you damage the rescue sub or hurt the rescue team what's the point of the rescue. They would take the extra few minutes necessary to put the submersible safely in the water.
Stupidity: Monk steals the magazine from Coffey's SIG. However, I don't see how he could have jacked the slide to eject the round in the chamber without being noticed. Someone as paranoid as Coffey was at this point would not have left the chamber empty. (Just FYI, when you load an automatic pistol with a magazine, you have to pull back and release the slide to load the first bullet in the barrel.)
Suggested correction: Since we are never shown that Coffey did chamber a round, we cannot assume that he did based on his personality alone. Therefore this isn't a plot hole. However, it is ridiculous that he is threatening people with a gun without a chambered round. This entry should be listed as "Stupidity."
SEALs don't carry weapons without a round chambered. The "maybe" here falls much more on the side of the round being in the chamber. And "Stupidity" wasn't an option available when this entry was originally submitted. :).
Corrected entry: There are no fish in the entire movie except the scene in the sub with the crabs on the dead guy. Phytoplankton are attracted to artificial lights which means a whole food chain develops around submarine structures like the Deepcore rig - just look at any film of the shoals of fish feeding around the legs of an oil rig. You'd think there would be fish in the ocean at least every now and then, but we don't see a single one.
Correction: Why? They're in a noisy, huge, lit up oil rig. That would drive most, if not all fish away from the immediate area.
Plankton are attracted to artificial submarine lights which establishes a thriving food chain around submarine structure like the Deepcore rig, and fish are not scared away by noise. Just look at the films of the shoals of fish feeding around the underwater structures associated with oil rigs.
Corrected entry: Just before Bud descends to disarm the warhead Lindsey asks him why it's he who has to go. His response is, "if not me, then who?" The answer's obvious: the Navy SEAL right next to him who's been thoroughly trained in deep-sea diving with the special breathing liquid and who would certainly know more about disarming nuclear warheads than a commercial diver.
Correction: As Bud says later - he 'always knew it was a one way trip'. It's a suicide mission and the Navy Seal, trained in the use of the liquid breathing gear, knows that too. So when Bud says 'If not me, then who?' he is asking who is willing to die in his place (though he doesn't want Lindsey to know that) and nobody is.
Also I believe that the seal injured his leg.
Correction: As a deep sea SAT diver I have worked on many rigs as in the film. The air pressure in the rig is the same as the water pressure. That's why the sea doesnt pour in through the moon pool. You can swim from the rig without a problem, I have done it many times with just a wet suit to stop the cold killing me. You cant swim to or from the surface though as you would change pressure to fast and your lungs would pop.