Visible crew/equipment: You can see mermaid's underwear after she is given only a shirt by Philip. Appears to have red in it which can be seen through the white shirt given to her.
Factual error: After the mermaids scene, when Blackbeard, Jack, and the others start walking through the next island to find the silver chalices, two distinct bird calls can be heard. Both are native to Australia - they are the Magpie Lark, also known as the Peewee, and the other is the Willie Wagtail. Both birds are not found anywhere remotely near the Caribbean.
Other mistake: In the mutiny scene where the cook is torched, the distance between the long boat and the Queen Anne's Revenge increases when the cook is only shown paddling away after the QAR turns towards it.