Hi,
We have been to St Maarten. It is a very dry climate and hotter than we expected. We went to Pinel Island and did a snorkel there which was pretty cool. You take a bus from the Dutch side to the French side. Then a motor boat drops you off at the island . Most of the locals are topless on the beach...no big deal but FYI in case it matters. The water is clear and the guides attract the fish with food. We saw a lot of fish. This tour was through the cruise line. Don't know what else is available there.