After you steal the Interceptor, you're supposed to proceed directly to Isla de Muerte to conclude the film-based part of the storyline. You're not supposed to use her to rush around the Caribbean doing sidequests. To discourage that, any time you go to Jamaica, the Dauntless attacks you. If you're in the Interceptor and the Dauntless attacks you, you're supposed to run away. You're not supposed to attack. If you get too close to Dauntless, it boards you, and with about 1000 crew compared to about 40 on Interceptor, the boarding action is, of course, a slaughter. But you've forgotten one important fact - I'm Captain Jack Sparrow. I'm wearing gold armour and so are all my officers, including Mr. Gibbs. The boarding crew, when they can be bothered to show up bearing in mind the crew disparity, are all wearing battle armour. We all have decent swords. The crew of Dauntless know what they're facing and are already at Low morale even before I give them a salvo of grapeshot. And so the action is indeed a slaughter, and we're the ones doing the slaughtering. The problem is that Dauntless doesn't surrender (it's probably programmed not to), and the few surviving crew plus the entire crew of Interceptor aren't enough to even swap to Dauntless, let alone take it as a prize. And so, after looting as much as possible... Incidentally, I was not immortal during the boarding. A couple of decks could be added to the times they almost caught Captain Jack Sparrow. So Dauntless never bothered me again when I went to Port Royale on sidequest business, though Norrington did resurrect himself so that the subsequent scenes involving him at Isla de Muerte and Port Royal went ahead as normal.