Factual error: The radio system in use at that time was based on spark transmission and we should never have heard a nice clean transmission of Morse code SOS or CQD beeps. (01:45:25)
Continuity mistake: When the musicians go out on deck to play as the ship is sinking all they have on is their uniforms. They are seen this way a few times, in the last shot of them they all have on overcoats. (02:06:30 - 02:22:30)
Continuity mistake: When the captain looks at the bridge sinking, the water level is by the middle of the helm wheel. In the next shot, from the other entrance, the level is lower than that, and in the next it's again by the middle of the wheel, which is also turned to a different position. (02:24:00)
Continuity mistake: When Jack and Rose are on the way up to the end of the ship, they go past a priest with lots of people praying, some are holding his hands, yet in the following shot, the people are not holding his hands, and are a bit further away from him than in the previous shot. (02:31:20)The-Immortal
Factual error: In the film the water tight doors are shown to lower mechanically all the way down, however in reality the last 20 inches or so they would suddenly drop by their own weight to effectively "dent" into the floor creating the water tight seal. A few of the crew in the film getting through "at the last moment" would have actually had their lower legs shattered by several tonnes of iron.
Factual error: At the end of the movie, the Straus' are seen lying in each other's arms on their bed with water coming into the cabin under the closed door as the ship is sinking. This is not true, their cabin was on C deck, but his body was found in the following days of the sinking. For his body to get into the open water it would have had to float through a closed door, and up several flights of stairs. Historically, they refused to leave the ship, and were last seen sitting in deck chairs. They were there when the ship sank on the boat deck. Her body was never recovered.
Continuity mistake: When Jack gets invited for dinner after Rose's rescue his hair changes between hanging down and tucked behind his ear alternatingly. There is another change after he puts Lovejoy's cigarette behind his ear. Similar alternating changes happen while he talks to Rose in the gym. (00:43:15 - 01:14:55)NancyFelix
Continuity mistake: When Rose and Jack beg a steward to open the gate for them while the water is rising, the steward drops the keys and runs away. There are two shots of the keys on the chain lying in the water arranged in totally different ways (the difference is not caused by the water flow as the keys are not moving in either shot). (02:18:55)NancyFelix
Continuity mistake: When the ships sinks and the back is rising, you see no people swim under the ship. When the ship breaks and falls down, the sea is crowded with people, who get crushed under the ship. (02:35:15)