Revealing mistake: When Captain Jack and Will are walking in the upside down boat, from the outside it looks like it's made of fibre glass rather than wood.
Continuity mistake: During the Black Pearl's ambush on Port Royal, they destroy a wall to the prison. Pirates in one cell manage to escape from a hole in the wall destroyed by one of the boat's cannons and Jack is stuck in his cell because the hole isn't big enough for him to fit through. As this happens, we can actually see the small hole when one of the pirates say "My sympathies. You've no manner of luck at all" as the other pirates escape the cell. Yet in the next shot as Jack is watching the other pirates escape, the small hole in Jack's cell is now smaller than it was in the previous shot.
Other mistake: When the Interceptor reaches the "boat graveyard" just off the dreaded island, it hits a pole or other assembly from another boat underneath them. It then "falls", literally plummets, downward and hits the ground with a thud. But wood doesn't "fall" downward through water, in fact, most wood swims. Even with other metal or other objects attached to it, this whole piece/assembly would have to be solid lead to "plummet" at that speed through water. No matter what the material is, it cannot go down that fast through water.
Continuity mistake: After young Elizabeth tells young Will "I'm watching over you", there's a strand of hair over his ear, which appears and disappears randomly depending on the shot.
Continuity mistake: Young Will lays unconscious by the edge of a blanket. When the angle changes there's much more blanket behind.
Visible crew/equipment: When Elizabeth is first taken aboard the Pearl you can see the yellow coloured contact lenses that Captain Barbosa is wearing.
Continuity mistake: Barbossa shoots Pintel and a hole appears in his shirt. This hole soon vanishes never to be seen again. (01:11:00)
Plot hole: Elizabeth goes to drop the medallion over the side of the Pearl. Barbossa and the crew gasp and take a step forward revealing they want/need the medallion thus giving Elizabeth the upper hand in the negotiations. Why not let the medallion drop into the water below the Pearl and simply "take a walk" to get the medallion off the ocean floor? The crew can walk under water as shown later in the film so this shouldn't be an issue. (00:38:15)
Suggested correction: Why not "simply take a walk" to retrieve that medallion? They have spent many years trying to find this bit of precious gold. If it's dropped, the underwater currents will most certainly carry it away, and if they walk underwater their feet will kick up the seabed making it even more difficult to locate. These cursed pirates have finally found their last missing piece, which would once and for all end their miserable curse, so they will not risk it being dropped into the sea.
Suggested correction: They only got startled from the idea, not realizing yet they could reclaim it easily, they are so close after all. Barbossa is not pleading to her, and they were hardly negotiating, Elizabeth was even only demanding they leave, nothing yet about the gold. All the scene does is give the dialogue needed for them to think her name is Turner, so they would keep her onboard and not just the gold. It's not an important part of the plot that they let her think she has the upper hand, if at all.
Other mistake: When Jack looks at the Pearl from his prison window, he is at least 10 boat heights above the ship. As we see throughout the movie when we look at the cannons of the Pearl and how they stand on the floor and shoot through the openings of the ship, there is no way that they could be rotated upwards to shoot as high as would be necessary to hit the prison cell.
Continuity mistake: Barbossa's scar changes appearance several times during the movie. At times it's almost completely gone, and sometimes it's even quite "thick".
Continuity mistake: In the overhead wide shot of the Pearl pursuing the Interceptor they are maybe three boat lengths apart. Before and after they are further apart. In general during that entire pursuit sequence their distances change too rapidly, from nearer to farther away (as seen from either ship towards the other), but that shot shows a particular discrepancy. (01:22:45)
Factual error: The scriptwriters revealed that they placed the story in a thirty-year environment set loosely between 1720 and 1750. Port Royal was destroyed by an earthquake on 7 June 1692, which had an accompanying tsunami. An initial attempt at rebuilding was again destroyed in 1703 by fire. Subsequent rebuilding was hampered by several hurricanes in the first half of the 18th century. I don't remember if the movie was set in a big, undestroyed Port Royal. However there was also set a huge fortress in Port Royal, which is definitely a factual error.
Suggested correction: This is also not the real world. It's set in an alternate reality which doesn't have to exactly match our reality.
Although the film series falls into the fantasy genre, it is set in a real period and place in history. Fictional events taking place in a historical setting is not the same as an "alternate reality." The anachronistic use of a real city as an important locale in the story is not artistic license, it is a historical error.
