We were at St. Thomas a year ago and booked a snorkeling trip through "Captain Nautica"....
One of the highlights of our cruise. Young, friendly staff who tooks us to some out of the way, protected reefs. We ended the trip on a very secluded beach out on Water Island; really a great time.
We were back on shore with time to climb to Blackbeard's Castle which gives you a great view and feel of the island. We did not try to get to the tramway which we learned form others ended up being packed with long lines.
Have a great time.