Carnival's Fascination Ship...?

My friend & I (ages 28 & 25) are going on a cruise in October to Nau & Half Moon Cay, Bahamas(5 day cruise). We want to go to Atlantis to swim with dolphins in Nau & also want to snorkel at some point... Any suggestions of where we should snorkel at? We are both super stoked, neither of us have ever been on a cruise before. Any other suggestions about the boat or either of the ports? P.S. How much are alcoholic drinks on the boat? :)