We did the Wave Runner Eco Tour (which was a blast) in December and we booked by telephone about two months out. Before you get your docs you should get a brochure in the mail about shore excursions; the number to call will be on the brochure. When we arrived on the ship the vouchers for the tour were in our stateroom. With that brochure you can also purchase gift packages and other things (wine, champagne) to have in your room when you arrive.