Factual error: The lake that Jack told Rose he went ice fishing on when she was threatening to jump is Lake Wissota, a man-made lake in Wisconsin near Chippewa Falls (where Jack grew up). The lake was only filled with water in 1918 when a power company built a dam on the Chippewa River, six years after the Titanic sank. (00:39:05)
Continuity mistake: When Jules is leaning against Michael's hotel door she is smoking a cigarette. When he opens the door she falls back and ash from the cigarette falls on her hair. Two shots later it is gone and her hair is rearranged while she is still on the floor. Then the ash reappears a few shots later.
Revealing mistake: Right after they "create" Leeloo and she is lying in the plastic cage with the little straps on her, the guy approaches her and says, "if you want out, you are going to have to work on your communication skills." She gives him a dirty look, and then you can see a huge hole, pre-cut in the glass, that she busts her hand through. (00:29:47)
Visible crew/equipment: Early in the movie, Melvin walks for the first time to the restaurant in which Carol works. As Melvin turns the corner on the sidewalk and walks towards the camera, he is surrounded by extras playing people he must dodge. If you look in the center and right background, you will see New York spectators standing in the middle of the street, watching the movie being made. (00:10:20)
Continuity mistake: After Nick becomes a hero, he wears a cast on his right arm. However, when he and Kate go to dinner with Kate's boss, Nick's cast mysteriously disappears for one shot. They are sitting at the table at the beginning of the dinner and Nick picks up a glass with his right hand, with no cast. The next time you see Nick, he has a cast on his right arm again.
Factual error: In one scene they attempt to divert the ship by manually activating the ship's bowthruster. A thruster is a propeller in a transverse direction. This allows the ship to turn more efficiently when docking. However the thruster loses any efficiency above approximately 5 knots. In the film they use it at 17 knots. Secondly, a thruster is powered by an electric motor of at least 500 kW, yet they manage to turn it by hand. That handle does not exist in real life, and no one would be able to turn it anyway.