We did Coral World and Coki Beach on our own. Found Coral World informative, and good snorkling near rocks on small Coki Beach. On our trip, St. Thomas was flooded with 6 cruise ships, so we didn't even want to try Magen's Bay (our table mates said it was very crowded--so we'll have to go again to see one of the world's 10 best beaches! LOL)