We booked the day before we docked. It was expensive at 95 dollars per person. We were taken to a boat with a few other groups. We were the first to go and it was very fun. You only get about 5 minutes up there, so for what you get I would not do it again anytime soon.
We did the Catamaran cruise and snorkel after lunch at Senor Frogs. They picked us up in front of the ship and we walked all the way back to senor frogs where the boat was. The boat ride took about 30 to 40 minutes and we had about 35 minutes in the water. The best part was the ride back. They had free drinks and dancing. I would go again if we visit nassau again.