As the large ship comes closer, our heroes make final battle plans. As soon as it catches up, Yates maneuvers his nimble ship into a position above the larger ship that allows the PCs to jump onto the ship's deck and attack the vicious looking crew.
A frantic battle ensues, during which some of the enemy soldiers attempt to magically knock our heroes off the ship, while they scramble to attach their tethers to the new ship. It's a close call, with several party members unconscious and barely revived by means of Goodberries. But in the end, the heroes, aided by Yates and Jebs' pet, prevail and conquer the crew.
Below the deck, they encounter and subdue the ship's cook (who happily offers his services to his new masters) and two poor but harmless souls that serve as the ship's human engines and don't even respond to the party.
They also find a mysterious box. After checking it for traps, they open it, only to unleash a Djinni that had been kept captive by the ship's captain. The party manages to convince the Djinni to help them, and in return hand over his box – which he swiftly throws over board.
The Djinni points them in the right direction, then bids them farewell and disappears in a puff of smoke.
NB: I don't quite remember if we got any specific info from the Djinni before he disappeared.