. . . . I would do it on your own! You can do it much cheaper and have more time at the beach than the excursion allows. I did Trunk Bay on my trip over Thanksgiving.
Once you get off the ship take a taxi to RedHook, from there take a ferry to St. John then a taxi to Trunk Bay.
Taxi to Red Hook $7.00pp
Ferry to St. John $14.00pp (round trip)
Taxi to Trunk Bay $7.00pp
Entrance Fee to Trunk Bay $4.00 pp
Trunk bay is BEAUTIFUL I think the snorkling and the water color is as good if not better than
Castaway Cay.
There is a small snack bar and shop at the beach as well as showers. You can bring your own snorkle gear or rent it there. We brought our own so I don't know about prices)
I think there maybe a ferry closer to where the ship docks but it's a longer journey on that ferry.
We had plenty of time to do all that, go back to ship afterwards and then take the skyride up to Paradise Point and have a drink while overlooking the harbor!
I have great pictures if you are interested.
Jeffrey
happy sailing!