Top 10 Reefs in Thailand
Thailand's reef diving is concentrated in two distinct regions: the Andaman Sea on the country's western coast, with its deeper water, stronger currents, and open-ocean encounters; and the Gulf of Thailand on the east, warmer and shallower, best known for affordable training and the island reefs of Koh Tao and Koh Lipe. Serious liveaboard diving in the Andaman reaches the Similan and Surin Islands and, in the right season, Richelieu Rock. All sites are on the interactive map.
1. Similan Islands National Park, Andaman Sea
The Similan Islands, eleven granite and coral islands 60 kilometres off the Phang Nga coast, were closed to all visitors from May 2016 to October 2018 to allow reef recovery after repeated bleaching and diver impact. They reopened with a revised management framework including daily visitor quotas and designated mooring sites. Hard coral recovery on the northern islands has been documented by DMCR (Thailand's Department of Marine and Coastal Resources). Best known sites include Fantasea, East of Eden, and Elephant Head Rock. Best season: November to May.
2. Surin Islands National Park, Andaman Sea
The Surin Islands, more remote and less visited than the Similans, have been similarly affected by bleaching but retain outstanding soft coral and fish life. The Surin Islands are immediately adjacent to the Mergui Archipelago in Myanmar and share its water quality and biodiversity. The Chao Lay (Moken sea nomad) community has traditional fishing rights within the national park, a governance arrangement unusual in Thai marine management. Best season: November to April.
3. Hin Daeng and Hin Muang, Andaman Sea
Hin Daeng (Red Rock) and Hin Muang (Purple Rock) are submerged pinnacles in deep water south of Koh Lanta, beyond the Phi Phi Islands. Hin Daeng is encrusted with brilliant red and orange soft coral; Hin Muang, Thailand's deepest known dive site, is completely covered in purple soft coral Alcyonaria sp. from the top at four metres to beyond fifty. Manta rays Mobula alfredi and Mobula birostris aggregate at cleaning stations on both sites. Best season: November to April.
4. Richelieu Rock, Surin Islands
Richelieu Rock is a horseshoe-shaped submerged pinnacle near the Surin Islands that is consistently rated among the top five dive sites in Southeast Asia. Whale sharks Rhincodon typus visit reliably during their seasonal passage through the Andaman (March to May). Harlequin ghost pipefish Solenostomus paradoxus, seahorses, and frogfish Antennarius sp. are found in the soft coral; schooling barracuda, snapper, and trevally aggregate over the top. Best season: March to May.
5. Koh Lanta, Andaman Sea
The reefs around Koh Lanta — particularly on its southern point, Hin Daeng, and on the eastern side's Shark Point (Hin Musang) — have recovered well from earlier bleaching and now support productive reef communities. Leopard sharks Stegostoma tigrinum rest on the sandy bottom at Shark Point, and giant moray eels Gymnothorax javanicus are resident in crevices. Koh Lanta has a cluster of dive operators with good liveaboard connections to the Similans. Best season: November to April.
6. Koh Phi Phi, Andaman Sea
Koh Phi Phi's Maya Bay was closed from 2018 to 2022 to allow recovery from the reef destruction caused by sustained boat anchoring and extreme overcrowding following its fame from the film The Beach. Reef health assessments since reopening show significant hard coral recovery on the bay's walls, and visitor management systems — limited daily entry, mooring-only anchoring — are now in place. The broader Phi Phi reef has leopard sharks, turtles, and productive soft coral walls on the southern islands. Best season: November to April.
7. Koh Tao, Gulf of Thailand
Koh Tao is Southeast Asia's primary dive training destination, producing more PADI Open Water certifications annually than almost any other single location in the world. Its gentle conditions, warm shallow water, and large cluster of dive schools make it a logical starting point. The reef quality is fair rather than exceptional — Sail Rock, a nearby pinnacle accessible by day trip, is the best site in the area — but for a first reef experience combined with certification, it delivers well. Best season: March to October.
8. Koh Lipe, Andaman Sea
Koh Lipe at the southernmost tip of the Thai Andaman coast is a small island with fringing reefs and access to the reef systems of the adjacent Tarutao Marine National Park, which has been less affected by bleaching than more northern sites. Whale sharks Rhincodon typus pass through in season. The island itself is a relaxed base combining beach holidays with productive reef snorkeling and diving. Best season: November to April.
9. Koh Bida Nai and Koh Bida Nok, Phi Phi
The two Bida Islands south of Koh Phi Phi Don have some of the best hard coral coverage in the immediate Phi Phi zone, with their southern faces having escaped the worst anchor damage that affected shallower sites. Blacktip reef sharks Carcharhinus melanopterus are regular on the reef flat; the walls have excellent sea fans and barrel sponges. Both islands are accessible by day trip from Koh Lanta and Phi Phi. Best season: November to April.
10. Anemone Reef, Andaman Sea
Anemone Reef, near the Similans, is a submerged pinnacle that takes its name from the carpet of magnificent sea anemones Heteractis magnifica covering its top section, along with their resident clownfish Amphiprion ocellaris. The pinnacle structure concentrates schooling fish including fusiliers Caesio sp. in large numbers, and the surrounding blue water regularly produces encounters with manta rays and occasional whale sharks. Best season: November to May.