An Thoi is regularly called the best diving in Vietnam: coral gardens and reef fish between roughly 10 and 35 metres, with wrecks and pinnacles among the southern islets. Conditions split by season, so operators run the exposed southern sites when it is settled and the sheltered northern ones off Turtle Island when it blows. The season runs October to April.
The warm, shallow waters are clear and calm, with rich and varied coral life on the seabed, and diving is the best way to explore life underwater around the island. Divers could encounter colorful reef fish, nudibranchs, moray eels, stingrays, pufferfish, cuttlefish, and octopus underwater.