Similan Islands

The Similans break Thailand's limestone habit: this Andaman archipelago is granite, its islands stacked with smooth house-sized boulders that continue underwater into swim-through dive terrain rated among the world's finest. Mu Ko Similan National Park, set up in 1982, protects eleven islands of blinding sand and glass-clear water - visibility runs to tens of metres in season - with the Sail Rock boulder above Donald Duck Bay serving the postcard climb. Divers come for soft-coral walls, rays and the season's chance of whale sharks; snorkellers get their share straight off the beaches. The park closes annually from mid-May to mid-October while the monsoon scours the sea lanes, reopening each October to speedboat day trips from Khao Lak and to the liveaboards that do the islands fuller justice. A daily cap of 3,850 visitors, set when Ko Tachai reopened in 2018 after two years closed for recovery, guards what makes it worth the ride. The name comes from the Malay word for nine, the count of islands before Ko Bon and Ko Tachai were added in 1998.

The landscape

• Sail Rock viewpoint - the boulder climb above Donald Duck Bay.
• The dive reefs - granite swim-throughs, rays and seasonal whale sharks.
• The white-sand beaches - blinding crescents against clear turquoise.
• The snorkel bays - reef fish in glass-clear shallows off the sand.

When to go

Open only 15 October to 15 May; February to April brings the calmest seas and best visibility. Book ahead - high-season day trips and liveaboard berths sell out.

Before you go

Speedboat rides are long, fast and hard on weak stomachs. Day-trippers share the same few bays at the same hours - liveaboards escape the rhythm. Visitor caps and no-plastic rules are enforced.

Nearby

Khao Lak's mainland beaches, the Surin Islands and Phang Nga province.

Key facts