If you are looking for great snorkeling... St Maarten is not the place. However this island is the most likely place where you will find some underwater sea life. The water here is fairly calm and clear (on most days). So it does make for a nice snorkeling day... just don't expect to see huge numbers and variety of fish.

Went to Tintamarre as part of Captain Alan's 4 hour Snorkeling trip, and the snorkeling was excellent -- great fish, great reefs, sea urchins, etc., etc. As I understand it, the island is a nature preserve and so you are not allowed to take anything, and I'm not sure if you're even allowed to land to explore the islan -- we did not, we stayed in the water -- but the snorkeling was great fun.

Took a private yacht charter to visit for 1/2 day. Beautiful white sand beach with nice contrasting red rock and green trees. Not too crowded as you can only get there by boat. Snorkeling is not that great but we are from Florida where we measure things against the snorkeling in the Keys. No facilities on the island at all so be prepared. Great place to hang on the beach for a day. Highly recommend if that is what you are looking for.

We visited Tintamarre Island with Francois from Captain Alan's, and while we didn't go on the island, we saw some of the most amazing creatures snorkeling just off the shore there - sea turtles and even a barracuda in the deep water! A must for natural beauty and great snorkeling!!!