We did a fun catamaran excursion on St. Thomas last month. We were on the Glory and booked through the ship. This excursion leaves from the dock by open-air bus and travels to Red Hook where we got on a beautiful, smaller sized catamaran. We sailed over to St. John and anchored just off a private beach for fantastic snorkeling. There were lots of awesome, colorful fish to see. Plus, you could swim over to the beach and relax, or just stay on the boat if you prefer. There was non-alcoholic drinks included going over. Coming back there was alcoholic drinks added along with a nice buffet. They played good music (not too loud) and the sailing was spectacular. When we returned, there was plenty of time for some shopping at the harbor.
I highly recommend this excursion.