Deliberate mistake: When Jack fights the impostor, they are roughly the same height, but when the impostor is revealed to be Angelica, she is suddenly much shorter than him. (00:21:30 - 00:23:50)
Revealing mistake: When Jack Sparrow is chased in London, being on the carriage and looking back to his chasers, you can see the broad tire tracks of a modern vehicle in the mud. (00:16:55)
Continuity mistake: When the movie ends, Barbossa is given his hat with no feather. A frame later the feather appears. (02:04:55)
Answer: The difference this time is that she actually kissed him before pulling him under. Either she breathes for him that way, or there's some magical property to a mermaid's kiss. They mentioned earlier in the film how a mermaid's kiss can save a man from drowning. Also, once the end credits start to flash on the screen (background is under water), about the 4th set, the screen lightens, and you can see two "mermaid" figures/shadows swimming toward the upper right of the screen. This is most likely Philip and Syrena. He became a "mermaid/merman."
Phixius ★