Goofs

(at around 50 mins) When Jane Edmunds gets called away from her station she pushes her headset down from her head onto her neck and walks away - only the previous shot shows that the headset is connected with a cable.

(at around 39 mins) When Harry and Norman are talking after the scene in the eating area, and Harry tells Norman they are going to die down there, Harry lies down in his bunk. The first shot shows Harry lying with his head on the pillow and the next shot shows Norman from Harry's perspective and his right foot is hanging over the bed. As the conversation ensues, Harry sits up in his bed and is clearly seen leaning against the wall, which means his legs should have moved up too. The next shot of Norman shows that Harry's right foot is still hanging over the edge.

(at around 1h 35 mins) Norman has determined that Harry is Jerry. He explains this to Beth then throws a book to her with his right hand. Change camera and the book is thrown from his left hand.

(at around 1h 30 mins) When Beth opens the cupboards to show Norman that there is no food, she opens the left door and then the right, and when she closes them the left door stays closed but the right one swings open a little bit. The camera cuts to Norman, and when it cuts back to Beth the left door is open and the right one is closed.

When they are debating whether to go or stay norman puts his hand on his chin but in the next scene it is open and away from his chin.

Harry tells Norman and Beth that they may not be far enough away from the explosion and that they may get sucked back in, even if they aren't destroyed by the shockwave. Massive underwater explosions do not cause a suction effect, rather, the water that has been displaced rushes in to fill the void, and it will rebound numerous times. Each rebound loses roughly 60% of it's energy, but will create multiple shockwaves. This is why underwater detonations are significantly more devastating than airburst explosions.

The crew used re-breathers scuba equipment. A re-breather allows you to breathe your own air over and over again and produce no bubbles.

In several scenes the team members wear various recreational dive computers, which are useless on a 1000ft saturation dive.

Beth calls the creatures that attack Norman, Belcher's Sea Kraits, but that's not what Belcher's Sea Kraits look like. Belcher's Sea Kraits are banded silver and black snakes. Those in the movie look like caecilians.

Ted mentions Pope Benedict and the artist Giotto. The real Pope that tested Giotto was Pope Boniface VIII.

(at around 52 mins) Ted sees Harry in the shower, and Harry is singing. He doesn't have on his voice adapter. So, Harry's voice should be very high, due to the helium in the air. However, his voice is perfectly normal. The voice adapter is the small box on the silver chain worn round their neck, the chain is clearly visible round Harry's neck.

(at around 31 mins) When Beth is accessing the Spacecraft's computer "Unknown Entry Event" is readable when reflected off her helmet, it should be mirrored.

When Harry (Jackson) is eating the eggs, he lists numerous spices he tastes. Some of the spices (Chervil especially) would not be that common on a Navy secret mission, for a stay of just a few days.

While in the Gravity Drive reactor room, as the "Burning Man" Edward Corrick is rising from the coolant on fire, the coolant is clearly flowing in reverse. This is an illusion to make it seem as though he is rising from the coolant on fire when in actuality he is sinking into the coolant.

Barnes clearly has an earring hole in his left ear, which is permitted for male US Navy personnel as of 2021, but proscribed by regulation at the time of the movie.

(at around 1h 28 mins) After Harry saves Norman when he has a valve leak and is attacked by a sea snake, there is a sky shot of Harry telling Norman to breathe normally. In the last few seconds of the scene you can clearly see in the lower left hand corner the leg of a crew member wearing shorts with black and white sneakers.

When Jerry first makes contact, he transmits in code : "MY NAME IS JERRY". Later, the code is revealed to have been mistranslated and the message reads: "MY NAME IS HARRY" If the letters H, E, J, and A in the simple letter/number substitution code were wrong, the first message would have read: "MY NEMA IS JERRY". Also, the entire series of conversations they had would have exhibited the same error, yet none did so. (HAPPY would have been JEPPY, ALL = ELL, etc.)

The team needs to decompress each time that they enter the sub/ habitat module/ spaceship while scuba diving, which at 1000 ft, actually takes ~15 hrs. There is no need to decompress on board the surface ship since the sub's interior air pressure is always ~15 psi (1 atm) during the entire ascent (and descent) - as are presumably the habitat module and spaceship.

(at around 18 mins) Oxygen is not a corrosive gas in the same family as fluorine and chlorine. Oxygen is still toxic, especially at such high pressures, but not for the stated reason.

(at around 14 mins) During the descent to the underwater habitat, Harry identifies the classical music inside the mini-sub as: "Mozart. Horn Concerto in E-Flat, K447.", which is not correct. It is Wolfgang Amadeus Mozart's Horn Concerto in D, K412.

(at around 26 mins) Just after the crew enter the craft Beth says that someone else must have been there because of the foot steps - she means foot prints.

(at around 42 mins) After Harry went in the sphere Barnes turned round and accused Norman of screwing up their trip to the surface in other words saying it was Norman's fault that they were not going up to the surface when Norman had nothing to do with it was Harry's fault due to Harry going to the spacecraft when they supposed to be up to the surface.