I'm taking a 7 day cruise in a few days to the W. Caribbean (Cozumel, Cayman, Ocho Rios) and have never been on a cruise before. I want to just go to the beach in Cozumel, snorkel in Cayman, and go to Dunns Waterfall in Ocho Rios. I've heard that if I book excusions ahead of time privatley, I can get a much better deal on them. Additionaly, if I book ahead of time, I'll have a spot reserved for myself, opposed to missing out if I wait too long. I get cold very very easily (I have a health issue). If its raining, or too cold, I don't want to go snorkeling or go to Dunns Waterfall. Should I still book ahead of time or just wait to book an excursion for when I get there?