Continuity mistake: At the start, when Elizabeth kneels in the rain in the background, just as Cutler Beckett's legs appear in the foreground, the floral edged row of chairs are beside her. When she drops her bouquet to run to Will, as the camera pans up the rows of chairs are farther back. (00:02:10)
Continuity mistake: When they dig up the chest and Will arrives, there are long shadows. Yet, when Jack, Will and Norrington duel, they have very short shadows directly beneath them. The large chest's shadow changes as well. (01:40:20)
Continuity mistake: When Jack and Gibbs walk on the dock towards the Pearl, they pass a couple kissing, as Elizabeth calls out to Jack. In the following shot, that couple is much farther (about 10 ft) up the dock, away from the Pearl - note the other ship's exterior, behind them. (01:17:00)
Continuity mistake: After Mr. Mercer kills Governor Swann's Captain friend, he heads for the carriage to search for Elizabeth. The candle in the carriage lantern differs between shots - note the height and melted wax. (00:26:50)
Continuity mistake: After the monkey throws Jack's hat overboard, Gibbs, Marty, Cotton, et al, run to look over the deck rail, when Gibbs shouts, "Jack's hat!" However, in the next shot it's not until Gibbs turns and shouts, "Clearabout!" that Marty, Cotton and the rest actually reach the deck rail. (00:17:10)
Continuity mistake: Aboard the Pearl, when Gibbs asks, "For the love of mother and child, Jack, what's coming after us?" as he walks towards Jack, the knot of his neck scarf is on his white shirt at his back. In the next shot, it is around his neck at the front. (00:17:00)
Continuity mistake: At the beginning of the film, right after Jack hands Gibbs the dead man's leg, Mr. Cotton throws Jack's coat about his shoulders, over his hair and bandanna, but when Jack turns around, in the next shot, his hair and bandanna are on the outside of the coat. No one touched them, and Jack seems oblivious to his various accoutrements, so he wouldn't have done this either. (00:06:50)
Revealing mistake: When the fruit from Jack's "kebob" lands next to him, they gently plop to the ground intact, despite having fallen from a great height. Although Jack also lands intact, his fall was cushioned by a number of obstacles - the multiple wooden bridges, the bamboo pole catching between the rocks, the unwinding rope, etc. With the exception of the pineapples, the already-damaged fruits (from being speared) are too thin-skinned or the rinds too brittle to have survived an impact from the height, speed, and angle shown. These are the SAME fruits (papayas, mangos, and melons) that easily splattered into pulp when thrown at Jack by the native women with far less force, a slower speed, and at a close range. (00:40:50)
Continuity mistake: In the scene when Jack loses his hat and it drops into the water the hat sides are more curled than when Jack had the hat on his head. (00:17:00)
Continuity mistake: When Will Turner is to be given the lashes by his father, his shirt is torn up the back, with only the collar remaining intact on the back of his neck. In subsequent shots, the shirt is completely off his neck, back and shoulders, even as seen from the front. After his lashes are completed, his shirt is shrugged back on, with the neck in the back intact again. (01:11:30)
Continuity mistake: When Elizabeth demands, "What are the charges?" the guard is just putting the shackle on her left wrist, with the right off as well. However, in the previous shot the left shackle is already on and the right is being put on. (00:03:20)
Continuity mistake: When Elizabeth, Pintel and Ragetti fight Jones's crew, Ragetti tosses Elizabeth the sword which she catches in her left hand, as she holds another sword in her right hand. She then tosses the sword from her right hand to Pintel, as she holds the other sword in her left hand. Next shot, when Pintel catches it, the sword in her left hand has disappeared - note her empty open hand, only to reappear in the next shot. (01:54:20)
Continuity mistake: When Jack is snatched up by the water wheel, as he stands in the open grave, he gets stuck in the wood blade positioned exactly between two wheel spokes. When the key falls from his neck there is a close-up of it getting caught on the nail. In the next shot, Jack is still trapped in the wheel, only this time he is stuck in the wood blade directly beside one of the wheel spokes. (01:52:30)
Continuity mistake: When Cutler Beckett enters his office and places the lantern on the desk, the handle is down. However, when Elizabeth walks out of the shadows, the lantern's handle is upright, then down again in a later shot. (00:27:30)
Visible crew/equipment: After Will is captured, when Jack first opens his make-up laden eyes, the white square reflections of the reflector shield is visible in his eyes; as it is in other characters' close-ups as well. (00:25:05)
Continuity mistake: In the scene when Captain Sparrow, Elizabeth, and Norrington dig up the chest and open it, we can see that there are documents filling the chest all the way to the top. The shot changes, and now you can see that there are fewer documents in the chest, even though they haven't started pulling them out yet. (01:45:05)
Continuity mistake: On the water wheel, the characteristics (such as shape and size) and position of the hole Jack created keeps changing, once Jack is free of the wheel. (01:52:15)
Continuity mistake: When Gibbs interviews potential crewmen in the Tortuga bar, things on the table change position between shots, and the height of the three candles differ as well. (01:07:30)
Audio problem: Just as the waterwheel begins to roll away from the mill, watch Will and Norrington on top of it - the sounds of their swords clashing doesn't synch up with their actions. (01:47:30)
Continuity mistake: When Will has been rescued from the Flying Dutchman and they go up on deck just before the kraken attacks, Will is on deck. A moment later he is seen on top of the mast, with no time to have got up there. The others who had come up from the cabin had only just emerged. (01:30:50)
Answer: The jar was to put Davy Jones heart in. He can't touch dirt ever again since he failed to keep up his duties which means he wouldn't be able to get his heart back.