I surfed a few places down there. If you google "Baie de L'Embouchure, Collectivity of Saint Martin, Saint Martin" in the maps it will take you there. A long paddle out, or a boat ride out will get you to a decent rock break. There are some places on the water that rent boards, and it you walk around the corner there is a nude beach. I remember there was a break on the north end that you had to hike to but never got around to it. also I stopped and checked out Guana Bay, and there were surfable waves there. Good luck!
St. Martin is a very cool place. very cosmopolitan. i was there a couple of years ago for a conference. rent a car and drive around the island - you can go from the dutch side to the french side and back in just a couple of hours. some of the roads are pretty crazy. lots of beautiful beaches. no real waves when i was there, but if you sail you can rent windsurfers/kites at orient bay. have fun.