You'll be there on my anniversary!
At Castaway Cay, they've got a nature tour water ski excursion. That was A LOT of fun! They take you around the island and tell out about it. We even had a good sized shark come right past us one of the time we were parked ou in the water (the average depth is something like 4 feet...which makes now me wonder how the boat docks there!). Be sure to get a Konk Kooler on the island. They're phenomenal and you'll find yourself missing it once you get back to the mainland.