Revealing mistake: When the [CGI] Titanic leaves the dock, watch a man in a green jacket close to the bottom part of the screen. He is waving goodbye to 'nowhere', for that part of the boat is empty and its prow is pointing away from where he is staring. This reveals he was looking at a green screen, with no idea whatsoever of what was going on. (00:25:40)
Continuity mistake: Ruth walks to the ship, followed by Rose and Cal. When she is about to enter, the angle cuts and suddenly several women with dogs haven taken her place, followed by a lady who looks nothing like Ruth. Then in the following close-angle the group is meters behind from where they first were, repeating the walk towards the door. (00:22:15)
Factual error: Shortly after Old Rose mentions just leaving the coast of Ireland, a shot of the captain's area (with the steering wheels) is shown with the sun shining in from the right (if facing toward the front of the ship) This would be impossible for a westbound ship in the middle of the day as the sunshine could not enter from the north side of the ship. The rest of the movie has all scenes with the sun correctly coming from the south during mid-day as the ship is travelling westbound.
Factual error: When Rose is trying to rescue Jack, the corridors that she is running through are a bright white colour, the lights appear to have a high colour temperature, and they have a more modern A19 bulb shape, and they might be halogen. In reality they would emit a much dimmer yellowish light. The lightbulbs would also be transparent along with a different bulb shape.
Other mistake: The ship is down by the bow about 30°. There follow scenes in which people make their way through flooded passageways. The water is chest-high, but level.
Revealing mistake: When Jack spreads the handcuffs over the pipe, we have a very clear close up shot of the links connecting the cuffs. In this shot you can see that the link nearest Jack's right hand is broken and not a complete link, therefore he should be able to separate the cuffs without going through the axe sequence. (02:00:05)
Continuity mistake: Just after Rose leaves Cal, we get an underwater shot panning down on Jack, showing that the window he's standing next to is fully submerged. However, interior shots after that show air around the upper edge of it. It's not trapped air: it's constantly bouncing around, in a wave-like pattern. (01:53:10)
Continuity mistake: In the "You jump, I jump" scene with Jack and Cal persuading Rose to get on a lifeboat, Rose embarks the lifeboat at the front, port(left side) side of deck top. Yet when Rose jumps back on the ship, she climbs back on in the middle, starboard(right side) of A deck where the windows change, running towards the bow to the Grand Staircase; while Jack is running towards the Stern from the Port front side of deck top. Jack enters the Grand Staircase from the port side of Deck top, and Rose enters the Grand Staircase from the port side of A Deck. (02:11:40)
Continuity mistake: When Rose leaves Jack's company to retrieve help, and goes to return with the axe, she stops at the stairway with the rising water and wedges the axe on the bars. The camera cuts to behind Rose to show her removing her outerwear, and the axe is still being held up by the bars but it's nice and straight, before and after this camera shot, the axe is propped in the bars crooked at an angle. (02:00:05)