I too plan on doing that the next time in St. Maarten, I've heard its an awesome excersion and it fills up fast. Last time we went to sign up for it and it was already full, so if you are thinking of doing it, do sign up early, on-line if you can. They now have a simular excersion in Nassau and we were signed up for that one, but it was cancelled due to high winds that day, so I sure hope to try it out myself sometime. Hope you do it and enjoy it!
We did it last December. It was a lot of fun, but hard work. You still have time to enjoy the beach in Philipsburg and some shopping, so bring a bathing suit and sunscreen. You can rent beach chairs and umbrellas.
This was my original question so shall answer it for anyone that is interested. If you get a chance to do this tour jump on it. It is well worth the investment and would do it again in a heartbeat. It is three hours of fun with a crew that makes everyone feel like a seasoned sailor.