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.
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. :).
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.