Factual error: When the men are checking the store room for Rose and Jack, the men are using huge battery powered bright white flash lights that look like they're from Jurassic Park. Back then they would have produced yellow light. The light used in the movie was a Short-Arc Xenon bulb, you can tell this by both the very high color temperature of the light and the center of the light has a "hole" in it where the actual tube is blocking the beam. Such technology was not around at that time.
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.
Continuity mistake: When Rose is trying to rescue Jack she spies a fire axe. Smashing all the glass out from the holder she grabs the axe and turns round. The next camera shot shows Rose standing in front of the case with almost all of its glass intact.
Deliberate mistake: In the scene at the start of the movie with the "authentic" piece of film, you can see a girl with a hat waving to the people at the ground. When the ship is leaving port in the film, she and others are in the same positions, only in reverse, because the first "authentic" shot is the same shot, only reversed.
Continuity mistake: In the scene where Rose breaks Jack's handcuffs, you can visibly see the stunt person not wearing suspenders as Jack does. This is an inter cut shot between the raising of the ax and the striking of the cuffs. Leonardo's stunt double is noticeable in other shots throughout the film.
Continuity mistake: Look closely at the location of Rose's beauty-mark the first time you see her at the dock. It is on the opposite side of her face during the rest of the movie.
Visible crew/equipment: When Jack and Rose are running away from Cal to the first class dining room, if you look at the glass you can see a black screen, a light, and a crewman.
Continuity mistake: When Jack and Rose finally come aboard the top of the ship after she rescues him they ask the Colonel if there are any boats left and he says "up that way" The woman on the left, who looks kind of pathetic, is then later seen on the life boat with Molly Brown. (They show her face right after Molly says the line "its your men out there") The life boat with Molly Brown in it was sent out before the scene with the Colonel, meaning that she must have gone on the life boat, swam back onto the ship and then back onto the lifeboat.
Factual error: During the drawing scene, 'Jack' is using modern square sided, pressed charcoal with numbers embossed in the side of it. In 1912, Jack would have been using vine charcoal which was round and made of 'charcoalized' willow twigs.
Continuity mistake: When the ship is about to leave the dock, there's a lot of people saying goodbye to the ones that are going to leave the city. In the following shots, you can see Jack and his friends playing cards inside the pub. If you look through the window you won't see anyone. In the next shot, when Jack leaves the pub, the crowd is there again.
Continuity mistake: In the early scene where Jack wins the tickets for the voyage, his hand-rolled cigarette is thin and almost done just before he shows his hand. About five seconds later, the cigarette is fatter and longer.
Factual error: When Jack, and Rose were trying to escape the rising water they were trapped by a locked gate. Jack and the crowd pulled up a bolted down bench to use as a battering ram. When they pulled the bench loose they showed a close up of the wooden floor shattering. The wood was pressed fiber board which would never be used as ship decking, not to mention, pressed fiber board wasn't invented until decades later.
Factual error: The hymn that they sing at the church service about "those in peril on the sea" has four verses. "Peril on the sea" was written in 1860 but the verses that have "protect them by Thy guarding hand" and "O Spirit whom the Father sent" were not written until 1937, and thus could not have been sung at the service.
Continuity mistake: When Jack is persuading Rose not to jump, Jack's shirt collar changes position several times, revealing his white t-shirt from a little to a lot.
Continuity mistake: Right before dinner, Jack and Rose are talking to the Astors, and Molly comes up from behind them, asking Jack to escort her to dinner as well. In the next scene, when Cal calls back to Rose, Molly is still walking up to them.
Factual error: When Rose, Jack and his friends come up to the boat deck while the ship is sinking, they ascend using the second class staircase and its exit on the deck. When Jack lets go of the door it is able to hit the side of the deckhouse. On the actual Titanic there were walls on the bow side of each door, which supported an overhang above the entrance. This is not included in many scenes in the movie.
Revealing mistake: Many scenes used computer graphics to show the length of the ship. Passengers were also added walking on deck. The shadows for the passengers don't always match.
Continuity mistake: The steel deck fittings at the bow of the ship change shape. During the flying sequence, the fitting nearest Rose's right foot changes from a curvy shape to a flat angled shape.
Factual error: A small one & probably only noticed by dog trainers like me. When the dogs are being brought on board, they are on leather leashes made by J&J Dog Supplies, invented in the 1970s. It is the type of leash preferred by professional trainers, who probably supplied the dogs for the movie, and is distinguished by the "braid" near the snap, rather than by a sewn or riveted section. J&J's website is: www.jandjdog.com. You can see the leashes there.
Factual error: When the stern (back) of the Titanic is rising into the air, there is one shot where it appears bone dry. Easily hundreds of gallons of water would have been pouring off the still wet hull.
Revealing mistake: When the ship tilts to a vertical position, you see people falling and hitting objects on the deck. In a close up of that, you can see that a black and bronze-topped capstan has wrinkles in it and bends when someone hits it.
Factual error: Rose mentions Austrian psychoanalyst Sigmund Freud's ideas on the male preoccupation with size to Bruce. However this is 1912, and Freud did not publish the work relating to this until 1920 in "Beyond The Pleasure Principle." Also, up until 1919, Freud relied solely on data from females.
Revealing mistake: When Tommy, Jack and Rose are trapped down the staircase with a lot of other people, during the shot where Fabrizio is running towards Jack, look on the right portion of the screen. You can see a kid with a hat on, being carried around by his mother, who deliberately grins at the camera.
Revealing mistake: When Rose is running in the hallways trying to find help for Jack when he is hand-cuffed, she finds a man and asks him to help her free Jack. She gets frustrated with him and says "listen" then hits him. In shots before you can look at the man's hand and it already has blood on it before he touches his face.
Factual error: When Jack and Rose are being chased by the bodyguard, they run through the ship's boiler room, prior to winding up in the car. Titanic was fueled by coal, and the boiler workers were called the "black gang" due to what happened as a result of working there. Yet Rose was wearing a pale dress which stayed pristine after going through the area, as did her shoes. She should have picked up at least a LITTLE soot along the way, at least on her shoes and the hem of her dress.
Continuity mistake: When one boat drives back to search for survivors, you can see the lightspot of one lamp turn around faster than the man who hold this lamp, so you know that the lightspot is not from the lamp of this man, but from a studio lamp. The man sees that himself and turns around very quickly to hold the speed of the spotlight.
Factual error: It is fairly well known that James Cameron built a virtual full-size replica of the ship for shooting the exterior scenes. However only the Starboard side of the ship was constructed; when scenes were required that need to show Portside Cameron employed a method known as 'flipping.' For example, in the early scenes of the film we see Titanic at 'Southampton' and passengers boarding the port side. This was achieved by reversing the camera angles. All the signs on passing carriages/vans and White Star logos were printed back-to-front so that when the scene was printed it could be reversed thus showing both sides of the ship! The problem is that in reality the Starboard side of Titanic was NOT a mirror image of the Portside. On one side of the forward boat deck there were entrances to the First Class Gymnasium and forward Grand Staircase, while on the other side there were the windows of the Officers' Quarters and the entrance to the Wireless Room. On Cameron's Titanic you get to see the gym etc. on both sides of the ship.
Factual error: The Master-at-Arms office, where Jack is handcuffed, was in actuality an inside cabin and had no portholes at all.