Grab a drink at the cafe right by the airport. It's pretty cool seeing how close the planes get.
There are two sides to the island. One side is French and the other is Dutch I believe. Both sides are nice, especially the beaches. But I think we enjoyed the French side more when it came to walking around and dining. There was one restaurant I can't remember the name of, but it was the best food I have ever had. Upscale French place on the beach...
The water can be cold early in the morning but it's like a warm bath in the middle of the day. There's not really any kind of Shark problem there, but watch out for sea urchins. If you step on one you will regret it for days haha.
I recommend going on a Catamaran scuba diving adventure. They take you and a group out for the day to all the best scuba diving spots and serve you drinks. Equipment was included I believe.