Thailand
The two-coast pick
Two coasts, two seasons: the Andaman's granite-island reefs and the Gulf's easy shore bays.
Thailand snorkels on two coasts that run on opposite clocks. The Andaman side — the Similan and Surin island groups, Phi Phi, and the Phang Nga coast — is the classic: granite boulders, coral gardens and big visibility in the dry, calm months, which is also when the national parks open. The Gulf side, and Koh Tao in particular, is the easy end of Thai snorkeling: shallow bays you wade into, warm water, and a calm season that falls in roughly the other half of the year. Thailand is not the place to expect untouched reef, and its busiest sites show real wear and real boat traffic — but the range is enormous, the logistics are simple, and the country has one honest trap worth naming up front: Phang Nga Bay and its James Bond island are a scenery-and-kayaking day, not a snorkeling destination.