Mu Ko Similan National Park

“Similan” means “nine” in Malay, and the park is named for the nine granite islands strung along the Andaman Sea about 70 km off the Phang Nga coast — Ko Bon and Ko Tachai were added later to the north. Routinely ranked among the world’s top ten dive sites, the Similans are the reason serious divers fly into Phuket and Khao Lak: visibility runs 20–30 metres, the water is a clear turquoise, and the granite seascape is unlike anywhere else in Thailand.

The islands split into two characters. Underwater on the east side, gentle coral gardens slope off white-sand bays — easy snorkelling among parrotfish, angelfish, turtles, and reef sharks in waist-deep water. On the west side, the park’s signature smooth granite boulders tumble into the sea and form the famous dive sites: Elephant Head Rock, with its swim-throughs, and Christmas Point. Further north, Ko Bon and Ko Tachai are the spots for seasonal manta rays and the occasional whale shark.

Above water, the landmark is Sail Rock (Hin Ruea Bai) on Ko Similan, island number eight — a giant sailship-shaped boulder you can climb for the postcard viewpoint over Donald Duck Bay. Most of the islands are otherwise sparse forest and powder-white beach, with no development and no fierce wildlife.

Insider Tip: A speedboat day trip ticks off the headline snorkel stops and the Sail Rock viewpoint, but the reefs are busiest from late morning. To dive the pinnacles properly — and to see them at dawn before the day boats arrive — a one- or two-night liveaboard out of Thap Lamu is worth the extra cost.

Watch out: The park is open in the dry season only, roughly November to mid-May, and closes entirely through the monsoon to let the reefs recover. Sailings are weather-dependent even in season, and the 500 THB national park fee is charged on top of the boat fare.

The islands lie about 1.5 hours by speedboat from Thap Lamu pier, the usual departure point near Khao Lak. Bring reef-safe sunscreen — ordinary sunblock is discouraged in the marine park — and expect a long, early start whichever boat you take.