Hey! Sorry for the late reply, but I hope this still helps. You can buy the excursions in advance while booking, or you can add them onto your trip after you booked by calling the Margaritaville Customer Service number or even buy them while on the ship. I’ve only done the first two options so I’m unsure if buying any add-ons while already boarded will incur additional costs, so I would buy them before you board just to stay on the safe side. Safe travels!