Plot hole: When Morgan and her Slave/New Boyfriend are escaping from the burning ship, which is going to explode any second, they emerge onto the deck, run up a flight of stairs, cross the deck to the stern rail, look about themselves, then dive overboard. They know the ship is about to explode and are desperate to get overboard. The railings are about a metre away from the hatch they emerge from in the first place - why not just jump overboard there?
Plot hole: Towards the end of the film, Morgan (Geena Davis) and Dawg (Frank Langella) are fighting to the death below decks, and Morgan pulls back a canvas sheet to show a cannon pointing right at Dawg's chest - and he stands staring at the burning fuse for a ridiculous amount of time, easily enough time for him to casually step out of the way and let the cannon blast away harmlessly. What an idiot.