The Similan Islands are an archipelago in the Northern Andaman Sea, off the western coast of Thailand, composed of 11 small islands renowned for crystal-clear waters, granite boulders, and rich marine biodiversity. Part of the Similan National Park, the islands are one of Asia’s premier diving destinations, attracting divers with colorful coral reefs, dramatic pinnacles, walls, and abundant tropical marine life.
Diving in the Similans offers a range of experiences suitable for all divers. However, strong currents can occur around popular sites like Richelieu Rock, while other sites around Koh Bon and Koh Tachai provide more relaxed diving conditions for less experienced divers. Expect encounters with manta rays, leopard sharks, whale sharks (seasonal), reef sharks, giant groupers, and schools of barracuda and fusiliers. Macro enthusiasts will also enjoy nudibranchs, frogfish, and ornate ghost pipefish among the coral gardens.
The Andaman Sea has two main seasons. High season (November to May) offers calm seas, excellent visibility (20–30 meters), and warm water temperatures of 27–30°C (81–86°F), making it the perfect time for liveaboard trips. Low season (June to October) coincides with the southwest monsoon, bringing rougher seas and limited diving access. Air temperatures range between 25–33°C year-round, with abundant sunshine in the high season.
The Similan Islands’ pristine beaches and towering granite formations make them spectacular above-water destinations as well, while the underwater world remains the primary draw for liveaboard travelers seeking vibrant coral reefs, pelagic encounters, and unforgettable drift dives.
Liveaboard Diving Regions :
Similan Islands
These islands feature stunning granite boulders, shallow reefs, and deeper drop-offs where large schools of fish, reef sharks, and occasional whale sharks can be seen. The sites vary from gentle drift dives to more challenging current-swept walls, suitable for divers of intermediate level and above.
Richelieu Rock
Considered one of Thailand’s top dive sites, this isolated pinnacle rises from 30 meters depth and is famous for frequent encounters with whale sharks, manta rays, barracuda, and schools of trevally. Currents can be strong, making it best suited for advanced divers.
Koh Bon and Koh Tachai
These islands feature sloping reefs, swim-throughs, and large granite formations. Koh Bon is famous for manta ray cleaning stations, while Koh Tachai offers drift dives with reef sharks and schools of jacks.
Western Andaman Drift Sites
Between the main Similan islands and the northern pinnacles, divers can enjoy exhilarating drift dives with pelagic sightings including leopard sharks, eagle rays, and occasionally whale sharks. Visibility is excellent in the high season, and the sites are ideal for divers seeking adrenaline-filled encounters.
