I second the horseback riding idea. Friends surprised us last trip by overlapping a few days and talked me into going horseback riding one morning. Normally I just let sand gravity set in. I do not remember the name of the stables but it was on the road to Le Galion Beach. We rode through a nature preserve and then onto the beach. Those that wanted to took the saddles off the horses, took off our shorts/pants leaving only our bathing suits on (which we wore underneath) and took the horses for a real swim in the ocean. No riding experience necessary and it was great fun. Our small group of 6 people ranged in ages from 10 to 60 and everyone had a great time. I've been coming to SXM for 30 years and it was one of my best experiences.