If you go to Trunk Bay with the Ship's excursion, you usually only get 1 1/2 to 2 hours there. If you want to spend more time, I suggest going it on your own, get off the cruise ship early and grab the ferry from Charlotte Amalie. I believe the ferry ride is 1 hr. 15 min. one way. Make sure to get back on time though! The ships excursion most likely includes the ferry ride, snorkeling gear and beach entrance fee. You can bet that it'll be cheaper on your own. Once you get there you won't want to leave. I was there on a rainy, cloudy day and I still didn't want to leave. For some though an hour or two on a beach is enough.