In the final battle aboard the Scorpion, Harris kills the same pirate twice.
Captain Kidd is shown as one of the pirate captains in 1700. However, in 1699 Captain Kidd was arrested in Boston, sent to England in 1700, and executed in 1701.
When Hawke compels Mrs. MacGregor to surrender the pistol she has hidden in her petticoat, it discharges. Yet, when she hands the pistol over to Hawke, the cock is still at half cock (essentially a flintlock's "safety"), and the frizzen is still back and covering the flash pan, revealing the fact that this pistol has NOT been fired. Had it been fired, both the cock and the frizzen would be in their forward (fired) positions.
Although the Mogul's ship accurately carries the Islamic crescent and star, a statue of the Hindu deity Kali is shown in the princess' cabin.
In the scene after the cannons are disabled, you can see an modern ship down in the bay.
In the last battle aboard the ship Hawke climbs one of the masts. The crow's nest at the top has a modern looking wire mesh guard around it, instead of the rope netting one would expect in an 18th century vessel.
Throughout the movie the pirate ships are shown as major warships, including two-deck ships-of-the-line; though most pirate ships were smaller vessels; usually converted from merchant ships. While pirates often increased their strength by capturing better ships; none ever had ships as powerful as many of those shown in the movie.
Molvina MacGregor's accent is very inconsistent throughout, veering between an Irish lilt to a Scottish brogue.