I just noticed this today. Sorry, I didn't get back to you sooner. We booked Bernards Tours in St Martin.
www.bernardstours.com We used him last year and many in our group thought it was the best part of the entire trip. It was $35pp and that included: a stop for souvies, a stop to look at and hold sea urchins, about 1 1/2-2 hours at the beach to swim, then to Maho beach (the beach at the airport), he times it so you can see the planes take off/land if at all possible, then another quick unexpected stop for a new camera (mine had an unfortunate run in with a wave)

, then back to the ship (there is still plenty of time to shop their also at the shops on the pier). And his van was fully stocked with beer, water, juice, soda, and rum punch (all free of charge). Of course the $35pp is w/o the tip. We tipped about $50 (2 families of 4 : $25 each family) So totally worth it!

. And in light of everything that has gone on at the other ports (robberies), I have to say that at no time did we feel one bit unsafe. His tours have a great reputation.