St Thomas is another port we've frequented, so we took a catamaran over to St John for snorkeling (the ship advertised it as the Champagne Cat). The young crew operating the boat were very friendly and helpful, and we had a wonderful time swimming around off Honeymoon Beach. Our daughter and other passengers didn't want to snorkel, so the crew ferried them to the beach to catch some sun using the cat's dingy. After we all returned onto the boat we had a light lunch and unlimited beer, rum punch, and soft drinks (I don't think champagne was offered). Definitely recommend this excursion!
We also shopped in the stores at the pier, where we got our liquor for home. It's duty free, but since we were in the US VI, you can bring more back home than in foreign ports.