You are going to love St. Maarten's! Someone recommended "Bernards tours" to you. Our son went on that tour, really enjoyed it. He took them on a tour of the island, stop at the beach where the jets fly over to swim for a bit, and then onto another beach. The cost was very resonable. My hubby and I went on a tour/beach break with "Island Marketing". We did the island tour, dutch and french side. A bit of shopping then onto "Little (Great) Bay Beach". It provided a lunch. The water was just the most beautiful blue I have ever seen and it wasn't over croweded. On the way back to the ship, we had the tour guide drop us off down town, where we did a bit more local shopping.
If your ship goes to St. Thomas, can I recommend "Sunny Liston Tours". It is by far the best excursion we have ever been on. He makes it fun as you tour the island, he has island music blasting from your ride ( open air multi passenger truck). You get a 2 hour beach break with that..I think it was $30 or $35. per person.
Have a blast on your cruise!
2003-Voyager of the Seas
2006-Voyager of the Seas
2009-Liberty of the Seas
2013 Carnival Breeze
Next adventure now on the SunShine!! WoooHoooo, cannot wait!