Northeast of Providenciales on North Caicos, the snorkeling at Three Mary Cays is considered to be very good. There are three small cays running to the northwest from the parking area access point. It is located at the west end of Whitby Beach.
To reach the snorkeling on Turks and Caicos by air, fly into Providenciales International Airport (PLS) located in the middle of the island. The island of North Caicos can be reached from Providenciales by charter snorkeling tour boat or by live-aboard boat. Also, there is regular ferry service provided by Caribbean Cruisin (25 minutes). In addition, keep in mind that Middle Caicos and North Caicos are interconnected by a causeway, albiet a rough road, so you can rent a car on one island to explore both.
Overall, Three Mary Cays is the 22nd most popular snorkel dive spot of all 32 snorkeling dives in Turks And Caicos.