Swashbuckling. If it takes me more than one round to cut a rigging line, grab it, swing down and boot a burly enemy off the side of my ship, something's wrong. Bonus points if you can do that while holding a beautiful woman in one arm.
Mostly, make sure you hit all the key cliches. Voodoo magic, ship to ship battles, 'good' pirates and 'bad' pirates, 'good' imperial fleets and 'bad' ones, haunted islands, dangerous seas, deadly perils, priceless treasures. Stuff like that.