Thailand

Diving Similan Islands

Granite boulder architecture in the Andaman Sea, with Richelieu Rock to the north for whale sharks and mantas.

The Similans are built of granite, not coral, and it changes everything about how they dive: house-sized boulders stacked into arches, canyons and swim-throughs on the west side, with gentler coral slopes on the east. Further north, Richelieu Rock is a lone limestone pinnacle in open water off the Surin Islands and the country's most reliable whale shark and manta site — a completely different dive that most Similan liveaboards fold into the same trip. Both sit in national park water, which sets the season by regulation rather than weather.

Know before you go

Best season

November to May. The marine park closes to visitors from roughly mid-May to mid-October each year.

Conditions

27–30°C, calm in season, visibility 15–30 m that drops when plankton blooms — which is exactly when whale sharks appear. Some sites carry current.

Getting there

Fly to Phuket (HKT), then 60–90 minutes north to Khao Lak or Tap Lamu for the liveaboards.

Dived with, here

• Thailand Divers

  A PADI five-star centre in Rawai on the south end of Phuket, running day boats to the local sites and trips north to the Similans.

What lives in Thailand

Recorded across Thailand rather than Similan Islands specifically — each page names the sites.