Off the northeast coast St-Martin, the snorkeling at Tintamarre Island is ideal for a full day adventure. Most snorkelers at Ile Tintamarre start at the main beach on the southwest corner near the boat mooring area where they enjoy all the reef fish and sea turtles. While the reef extends far of this beach, make sure to drag along a diver-down buoy so the heavy boat traffic can spot you. Next, head to the south coast into an area called The Lagoon where the barrier reef protects the snorkelers at low tide. On the far northeast coast, there is a good cove that very adventurous snorkelers enjoy.
To reach the snorkeling on Saint-Martin by air, fly into Princess Juliana International Airport (SXM). Note, there is a $30USD departure tax collected at the airport.
In addition, there is a ferry called Great Bay Ferry that interconnects St. Martin with St Barts.
Overall, Tintamarre Island is the 10th most popular snorkel dive spot of all 10 snorkeling dives in St Martin.