never been on a cruise but I have been to nassau and St Maarten. I like St M better than Nassau, it's a strange island 1/2 french and 1/2 dutch. you drive around and all of a sudden you cross a line and the language on the shops changes...drive more and you come back to the other language.
If you get the chance go by the airport when one of the Air France 747's is landing, just dont stand on the beach at the end of the runway of you'll be sorry.
thats not a photoshop thats the real deal.
I cant say what to do really, i know you only get limited time off the ship. One of my best vacations ever was to St Maarten
watch out for the nude beaches LOL..Cupocoy and Orient Beach i know of for sure. We ended up meeting a local guy there and becoming friends with him, he showed up around the island and even came and found us at our hotel when we had too many drinks and my gf left her camera in his cousins cab the night before.
Back to Nassau, it's nice and all..go check out The Atlantic resort, we stayed there for a few days, very cool hotel, even had a waterslide that goes right through the shark tank and a pretty cool walk through aquarium. If it's still there you can go to Blue Lagoon Island, they have a dolphin swim program , we got to swim with a momma and baby and also mess around in shallow water with the dolphin from the flipper movie they made a few years ago.
http://www.dolphinencounters.com/
they also had a place called sting ray city but I think it's closed now because of hurricane damage. you could go dive and feed the stingrays. i did the one in the cayman Islands and it was really cool except i got bit by a yellowtail snapper LOL