Continuity: Early in the film Bud throws his wedding ring down the latrine and then retrieves it with his right hand so it is covered with the blue disinfectant. In a (much) later scene, Bud has a blue right hand, despite not having had one in the intervening period.

Visible crew/equipment: During Bud and Coffey's fight in the lab, we see a lightbulb swinging from side to side between the two men. If you look closely, you can see a hand (belonging to a third person) pushing the lightbulb. The only people in the room are Bud and Coffey.

Visible crew/equipment: Watch the special edition version of the movie. During the scene when the crane is falling down on top of the sub, the camera is following people around the passages. When it comes to the end of a hall, and a hatch is shut in our face, we can see the shadow of the camera equipment in the door.

Continuity: When Bud is giving his wife CPR and starts to slap and yell at her you see her blink and swallow before they have any life readings. You also catch her closing her mouth as if to wet it when he bends over her body.

Continuity: When Lindsay is pulled from the pool after she drowns her wet hair is covering her face. In the next shot she is laying on the floor and Bud is smoothing her hair back to give her CPR. The shot changes again and her hair is back covering her face like it was when they pulled her from the water.

Factual error: Near the beginning there is a scene were 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.

Continuity: When Bud sneaks on Coffey in the moon pool, they are seen fighting. During this Bud shirt gets wet and rides up his back. In some shots it goes down again, but then goes right back up.

Continuity: When Jammer is alone in the derelict sub and the alien appears, all the electrical devices shut down, as they do in the whole movie. But in the close up shots from the side of Jammer, you can see the light at the top of his helmet is still on.

Other: During the submarine interior scene, there are several dead seamen shown floating about. One of them is pretty close to the camera and floating with his eyes open. He blinks before the shot ends.

Continuity: When Linds says "I got it. It's headed straight for us," Bud looks out the front window. Watch the umbilical because it doesn't start to move until a split second after the camera is in full frame.

Continuity: When Bud leaves Jammer behind in the sub, he gives him a strand of rope to keep the two connected. At first Bud keeps the bundle of rope and hands Jammer the loose end, however in later scenes it's shown that Jammer holds the bundle of rope and Bud holds the loose end; as Jammer is feeding him line.

Audio problem: When the crew are running around the passages, a guy with a beard yells something at Bud, and then uses a fire hydrant to put out a small fire. Funny, it doesn't make a noise.

Plot hole: Granted, Coffee is suffering from "high-pressure nervous syndrome," but if you're a Navy SEAL, wouldn't you notice whether or not your pistol has a magazine in it? Monk pulls the clip out of his jacket and starts knocking rounds out of it for the rig crew's benefit; the same dramatic effect could have been achieved with a handful of cartridges he could let slip through his fingers. You could argue that Monk didn't have enough time to unload the gun and replace the magazine, but in that case, I think the scene where Monk briefly had the gun should have been a bit longer. (Even had the empty magazine been IN the gun, Coffee still might notice the difference in weight, but that would be easier to suspend your disbelief for.)

Revealing: After the water tentacle sequence, Coffee brings Schoenick back to their bunks to get the submachine gun, so they can take over the rig. The bag containing the gun is stashed behind some pipes up by the ceiling. Watch when he reaches behind the pipes to grab the bag--the pipes move at least six inches.

Continuity: When Bud and Lindsay are in the sub after the big chase, water leaks in and Bud searches for something to fix it. He delivers some dialogue while opening (I believe) a first aid kit. The camera angle switches to Lindsay as she says something, and Bud can be seen in the background opening the kit once again.

Continuity: Bud swims to the moon pool and tries to sneak up on Coffey. Coffey aims a gun at Bud. Bud's right eye is swollen. In the next scene its not, and the following scene it is.

Continuity: During the scene after the water tentacle is discovered, the whole crew has a meeting. At this time, Coffee is cutting his right arm under the table. In the following scenes, his arm shows no signs of any cuts.

Factual error: When Lindsay is being revived after Bud towed her back to Deepcore, I understand why the CPR being done isn't exactly correct(due to the fact the actress isn't really dead) but the filmmaker neglected to notice that when the crew proceeds to shock Lindsay, she is wet and on a metal floor. Not only would she be shocked, the entire crew around her would be shocked as well.

Other: When the water tentacle enters the rig, in one shot in the 4:3 version of the film on video you can see that the tentacle is a superimposed special effect because of the dead straight line where it is supposed to have come out of the water.

Continuity: When the SEALS take over, they lock up the crew. After closing the door on Ed Harris and the shouting Mary Elizabeth Mastrantonio, one of the SEALS hangs a hat over the spyhole. The next time we see the door, the spyhole isn't covered.