We only got on and off the ship in Ft. Lauderdale. We did not do any excursions.
Seahorse Sailing and Snorkeling - NSE6. $49pp and well worth the cost. We enjoyed this excursion. They provided all necessary equipment.
We loved St. Maarten island. We took a water taxi from the ship to the Dutch side of the island. The beach was beautiful. I loved all of the local shops and open market areas. You can get some great deals on your purchases in St. Maarten. They will negotiate their sales price, which I love!
We did a self-guided tour of St. Thomas taking a local taxi to and from the ship. It struck me that St. Thomas did not appear as clean an area as it did 9 years ago when we last visited the island.