 FACT: In the sequence in which the Black Pearl is attacked by the  monster, Will Turner forces his knife into a sail to slide safely to  the deck. Sails of that period had horizontal reef bands which were  three to six times thicker than the sail itself, and the knife would  have popped out of the sail when it hit such a band (this was tested  on _"MythBusters" (2003)_ (qv)).