My wife and I have been going to SXM for about 10 years and I did my certification dives in St, Martin (79 degrees and 60' viz is better than needing a hood and 7mm wetsuit with 12" of viz). I have used both Dive Safari (Simspson Bay) and Ocean Explorer (Dutch side between the Royal Palm and the Atrium-on the beach). Both dive shops send a divemaster with you and the boats max out at 6 or 7 divers. There is a reef area on the Dutch side plus a collection of wrecks (and a sunken bridge). I've seen Hawksbill turtles, reef shark, eels, lobsters, shrimp and a variety of fish. It may not be overwhelming but a good variety.
You can get from one end of the island to the other in about 30 minutes, so where you stay is not critical to exploring the island. Grande Cas has at least a dozen very high quality restaurants. Since that is on the French side of the island, they charge in euros, although a few restaurants may be giving a $1 + 1 euro exchange. We like Spiga and have had very good meals at Bistro Caribe and Tastevin. There are also a variety of restauants at the marina in Marigot (French side capital). Tropicana rstaurant is high end and very good (French side tends to eat late--8:30 or 9 rather than 5:30 or 6).
On the Dutch side there are several very good restaurants at the Atlantis casino. Also, at Maho (near the airport) there is Cheri's for burgers and entertainment.
For entertainment you can race 12 meter yachts. They operate out of Bobby's Marina in Phillipsburg. You are part of the crew and the boats include Stars and Stripes and several Canadian boats that raced in the Americas Cup. there are also zip lines near Pic Paradis.
I suggest that you go to Travel Ralk onLine and find the St. Martin forum. It is an active forum that will respond to your questions.
Have a wonderful time.
