On St. Maarten, we rented a car and drove around the island. Enjoyed seeing France, and chased down a few Geocaches along the way.
But without doubt.... the best part was sitting on the beach at Maho Bay watching the airplanes landing! The final approach course is directly over your head,
and you will be only feet away from the aircraft! A terrific thrill, and great pictures! (Google Maho Bay to see what I mean!)
We enjoyed it so much, we are going back in February (same cruise/ship as you!)