On the northshore of St Barts east of the airport, the snorkeling at Anse De Lorient (aka Lorient Beach) is popular for its sea turtles.
To reach the snorkeling on St Barts by air, you will need to fly into St Barts Airport (SBH) on the northwest side of the island. To reach St Barts Airport, there are regular flights from either St Maarten (SXM) and San Juan Puerto Rico (SJU).
In addition, there is a ferry called Great Bay Ferry that interconnects St. Martin with St Barts.
Overall, Anse De Lorient is the 4th most popular snorkel dive spot of all 4 snorkeling dives in St Barts.