Diving in Similan Islands
Thailand's Crown Jewels — World-Class Liveaboard Diving
Why Dive Similan Islands?
- Consistently rated among the world's top 10 dive destinations
- Visibility regularly exceeds 30 metres
- Dramatic granite boulders, swim-throughs, and drop-offs
- Whale sharks, manta rays, and hammerhead sharks
- Richelieu Rock — possibly the single best dive site in the world
Thailand’s Similan Islands — whose name derives from the Malay word for “nine” — are a diver’s Eden. Set 70km offshore in the deep Andaman Sea, these nine granite islands are surrounded by some of the clearest, most biodiverse water in all of Southeast Asia.
The Similan Experience
The park encompasses sites ranging from gentle sloping reefs perfect for Open Water divers to dramatic granite boulder formations with swim-throughs, crevices, and walls plunging to 30+ metres. Elephant Head Rock (Hin Pousar) on Similan Island 8 is the showpiece — a labyrinth of enormous boulders creating a complex of channels, arches, and swim-throughs teeming with reef life.
Koh Bon and Koh Tachai, just north of the main Similan group, are where the genuinely big stuff happens. Manta rays, whale sharks, hammerhead sharks, and massive schools of pelagic fish are regular sightings from January through April.
Richelieu Rock
Just outside the Similan park boundary, Richelieu Rock near the Surin Islands is a horseshoe-shaped seamount that breaks the surface at low tide. Below, every centimetre of rock is encrusted with soft corals in vivid purples, reds, and oranges. Whale sharks are encountered here more frequently than almost anywhere else in Thailand, and the overall density of marine life is staggering — harlequin shrimp, ghost pipefish, frogfish, sea horses, and clouds of anthias coexist with whale sharks, barracuda, and trevally hunting in the current.
Liveaboard Diving
The Similans are essentially a liveaboard destination. While a handful of speedboat day trips operate from Khao Lak during peak season, the islands are best explored over multiple days on a live-aboard vessel. Most itineraries run 4–7 nights, covering the Similan park plus Koh Bon, Koh Tachai, and Richelieu Rock.
Dive Conditions
- Best season: November–April (park closed May–October)
- Water temperature: 26–30°C
- Visibility: 20–40m
- Currents: Moderate to strong at exposed sites
- Minimum cert: Open Water recommended; Advanced OW for some sites
Dive Sites in Similan Islands
Getting There
The Similans are accessible primarily by liveaboard from Khao Lak (2.5h north of Phuket airport) or from Phuket itself. Some day-trip speedboats operate from Khao Lak during peak season. The park is closed from May 15 to October 31 each year.