(at around 14 mins) At the beginning, just after the collision, the surviving characters are seen drifting on the ocean on a wooden platform. George Kennedy's character is plainly visible lying down with the group, even though he hasn't yet been pulled out of the water. He appears from below the water about two minutes later.
(at around 44 mins) When we first see the hard candy jar sitting on the shelf, each piece of candy is wrapped in cellophane. When the jar is opened, each piece is unwrapped.
(at around 12 mins) At the beginning, when the Death Ship is steaming full ahead at the cruiser, it is twilight. However, in the shots of the cruise ship it is clearly nighttime.
(at around 24 mins) When the wire that lifts Jackie up the air is shown on the deck it is run through a loop with no sort of release mechanism present. However, after a few frames of him in the air you see that it now has some short of release mechanism for dropping him. Also, when the noose first tightens it is around his ankle, but after he is dipped you can see that the line is actually run down to his waist (really noticeable as he is rotating).
(at around 1h 20 mins) Towards the end when Marshall jumps out of the hatch to tackle Ashland he is jumping towards the outer railing, but when the camera angle changes his movements are in the opposite direction. Even assuming the he over jumped and passed Ashland, the hatch that he jumped out of would be visible behind him, but it is not. The struggle was obviously shot at a different point along the ship than where the hatch was located.
(at around 15 mins) Early on, in the escape boat, survivors find something white floating several inches or feet below the ocean surface. They pull 'it' up, and it's the ship captain. He would have been dead after floating hours below the surface.
In the 86th minute, a voice from the ghost ship says 'posizione.' This is not German.
(at around 20 mins) Early on, when the survivors move from the escape boat to the derelict ship, all move to the ship except for the injured captain and one other crew member, who calls back another crew member to the boat to assist with the extrication of the captain. Very unrealistic.
(at around 20 mins) While two other characters are carrying the captain (George Kennedy) up the steps onto the derelict ship and they fall into the water, the captain is an obvious body double because he's wearing a thick gray wig and Kennedy is balding.
(at around 1h 1 min) When Nick is trying to free Lori from the shower by smashing the glass door, you can clearly tell that he is hitting the metal part of the door with the board and not the glass.
(at around 1h 16 mins) When Marshall is searching the meat locker where the bodies are hanging, despite all the bodies being covered in ice indicating that it is extremely cold inside, Marshall's breathe never shows as it ordinarily would.
(at around 1h 18 mins) When Marshall drops the anchor to stop the ship so that they can make their escape, the overhead shot of the anchor falling into the water clearly shows that the ship is not moving.
When Treavor and several passengers are exploring the ship early on, Trevor opens a sailor's unit where, over the bunk, there is loosened cotton batting. Presumably, this is meant to be spider webs.
When Ashland enters the bridge for the last time the captains chair has disappeared, but is shown again once the ships takes control of itself to ram the other ship.
The ship's bridge's ceiling is unrealistically low, and looks like the ceiling of an office building. The ceiling of the bridge is two or three inches above the tallest crew's heads.
There are numerous spider webs throughout the derelict vessel, yet after 55 year roaming the ocean the ship would not likely have any food for spiders.
When the survivors on the raft first come upon the ghost ship, in a long shot of the ghost ship, a helicopter is visible flying away in the background.
Throughout the cruise ship evacuees' time on the derelict Nazi vessel,you hear 1930's (?) English music playing. It would not be English, but rather German music which would be played.
(at around 51 mins) There is a sequence in which the character played by George Kennedy emerges in a dark uniform atop the ship while the character played by Richard Crenna looks from below. During three separate long shots of Kennedy, a crew member and camera are plainly visible on the left side of the shot.
(at around 16 mins) When the group first comes up upon the ship after it sunk the cruise ship, you see one of the windows open up, you can clearly see a person's arm when he opens the window, it is supposed to be opened by a ghost, which it clearly isn't.
(at around 1 min) Cameraman's shadow visible in the beginning.