Sword fight against other captains of different skill-levels. If you get close enough to an enemy ship you can choose to jump over to that ship to challenge the captain in a sword fight, the enemy captain can of course do the same. The fight could take place on the port- or starboard side of the main deck while the crew sits on the cannons and cheer. With upgrades and a skill point system sword fighting could by one of the skills you could add points to when levelling up.