Similan Islands

Discovering the Similan Islands

The Similan Islands exist on a schedule that the rest of Thailand does not follow. For five months of the year — mid-May through mid-October — the archipelago is closed entirely. No boats, no visitors, no exceptions. The Thai government shuts the national park gates so the monsoon can scour the reefs clean and the marine ecosystem can breathe without human contact. When the park reopens each October, the underwater world that greets you is the result of that enforced rest — coral gardens rebuilt, fish populations replenished, and visibility that stretches beyond 30 meters into blue water so clear it erases the boundary between floating and flying.

I took my first Similan speedboat from Tab Lamu Pier on a Tuesday morning in early February. The crossing from Khao Lak took ninety minutes through open Andaman water, and when the engines cut at our first snorkel stop off Koh Payu (Island 7), I looked down and could see individual coral polyps in five meters of water from the surface. A hawksbill turtle drifted below the boat, entirely indifferent to the ten snorkelers scrambling with their masks. Within three minutes of entering the water I understood why divers talk about the Similans the way they do — this is not a reef system you describe with adjectives. It is one you remember in silence, replaying the images behind closed eyes on the boat ride back.

The nine granite islands that make up the Similan archipelago sit 70 kilometers offshore in the Andaman Sea. Each is numbered — locals use the numbers as often as the names — and together they form a marine national park that has been protected since 1982. The granite boulders that define the landscape above water continue below, creating underwater swim-throughs, caverns, and walls colonized by sea fans, soft corals, and barrel sponges large enough to sit inside. The combination of warm water, seasonal closure, and strict national park enforcement has kept these reefs in a condition that most dive destinations lost decades ago.

What Makes the Similans Different?

The Similans rank consistently among the world’s top ten dive destinations, and the reason is straightforward: seasonal closure works. While reefs across Southeast Asia suffer from year-round tourism pressure, bleaching, and anchor damage, the Similan reefs get five months of uninterrupted recovery every monsoon season. The result is coral coverage and fish density that veteran divers compare to the Maldives or Raja Ampat — at a fraction of the cost and travel time.

The archipelago splits into two distinct diving environments. The east side of the islands faces sheltered water with hard coral gardens, gentle slopes, and the kind of visibility that makes underwater photography effortless. This is where day-trip snorkelers and newly certified divers explore — sites like Koh Miang’s house reef and the channel between Islands 5 and 6, where reef sharks patrol sandy corridors between coral bommies. The west side faces the open Andaman, and the underwater landscape changes dramatically: massive granite boulder formations create swim-throughs, caverns, and walls that drop to 30-plus meters. Elephant Head Rock, between Islands 7 and 8, is the signature west-side dive — a labyrinth of granite corridors where leopard sharks rest on sand ledges and gorgonian fans the size of cars filter the current.

Beyond the main nine islands, liveaboard itineraries extend north to Koh Bon, Koh Tachai, and Richelieu Rock. Richelieu Rock is widely considered the best single dive site in Thailand — a horseshoe-shaped pinnacle rising from the open ocean that attracts manta rays year-round and whale sharks between February and April. Day boats from Khao Lak cannot reach it. That exclusivity is what separates a Similan day trip (which is excellent) from a Similan liveaboard (which is transformative).

What to Do at the Similan Islands

Donald Duck Bay Viewpoint (Koh Similan, Island 8) — The most iconic image in the archipelago. A 15-minute scramble up granite boulders leads to a viewpoint overlooking a crescent bay named for a rock formation that vaguely resembles the cartoon character. The view from the top — white sand, turquoise water, jungle canopy, granite monoliths — justifies the climb. Included on most day trips. Free with national park entry (500 THB / $14 park fee, typically included in tour price).

Snorkeling at Koh Miang (Island 4) — The park’s primary visitor island, with a beach lunch stop, ranger station, and the best shore-accessible snorkeling in the archipelago. Wade in from the beach and within 30 meters you are floating over hard coral formations teeming with parrotfish, angelfish, and clownfish tucked into anemones. Sea turtles feed in the seagrass beds on the east side. Included on day trips.

Elephant Head Rock Diving — An advanced dive site between Islands 7 and 8, where massive granite boulders form a submerged labyrinth of swim-throughs and caverns. Leopard sharks, white-tip reef sharks, and moray eels inhabit the corridors. Depth ranges from 12 to 30 meters. Current can be moderate. Accessible on liveaboard itineraries and some advanced day-trip dive boats. Two-dive day trips from Khao Lak cost 4,500-6,000 THB ($128-170) for certified divers.

Richelieu Rock Diving — A submerged pinnacle 60 km north of the main archipelago, reachable only by liveaboard. Manta rays are year-round residents. Whale sharks pass through February to April. The rock is covered in purple and orange soft corals, and the marine density is staggering — seahorses, harlequin shrimp, octopus, and clouds of glassfish surround the pinnacle at every depth. Many divers consider this the single reason to choose a liveaboard over a day trip. Included on 3-4 night liveaboard packages (15,000-45,000 THB / $425-1,280).

Sunset Beach Camping (Koh Miang, Island 4) — The national park offers limited tent camping and basic bungalows on Koh Miang. Accommodation must be booked in advance through the Thai National Parks website. Tents cost 600-900 THB ($17-26) per night; bungalows 1,000-2,000 THB ($28-57). The experience is bare-bones — shared bathrooms, no air conditioning, generator-powered electricity — but waking up on the island before the day-trip boats arrive, with the reef to yourself at dawn, is worth every compromise.

Day Trip vs. Liveaboard: Which Should You Choose?

The day trip is the right choice for snorkelers, families, and anyone who wants a taste of the Similans without committing to multiple days at sea. Speedboats depart Tab Lamu Pier at 8 AM and return by 5 PM, covering 3-4 snorkel stops, a beach lunch on Koh Miang, and the Donald Duck Bay viewpoint. The pace is brisk but the quality is undeniable — you will see turtles, reef sharks, and coral that rivals anything in the Andaman. Cost: 2,200-3,500 THB ($63-100) per person, everything included.

The liveaboard is the choice for certified divers who want access to sites that day boats cannot reach. A 2-night trip delivers 8-10 dives across the full archipelago, including west-side boulder sites, Koh Bon (manta rays), and Richelieu Rock (whale sharks). You sleep on the boat, eat on the boat, and spend your days descending into water that gets more spectacular with each dive. Sea Dragon Dive Center and Wicked Diving in Khao Lak are the most reputable operators. Prices range from 15,000 THB ($425) for a two-night trip to 45,000 THB ($1,280) for a premium four-night expedition.

Where to Stay for the Similan Islands

There is no resort accommodation on the Similan Islands — only the national park’s basic camping and bungalows on Koh Miang, which must be booked in advance and sell out months ahead during peak season. The practical base for Similan access is Khao Lak, the quiet Andaman coast town 60 km from Tab Lamu Pier where all Similan boats depart.

• Walker’s Inn (Khao Lak) — Budget guesthouse on the main road in Nang Thong. Clean rooms, air conditioning, hot water, and an owner who is a former dive instructor. Walking distance to restaurants and dive shops. 500-800 THB ($14-23) per night. Best option for backpackers who spend their money underwater.

• Khao Lak Bhandari Resort — Mid-range resort with a large pool, spa, and garden bungalows. A five-minute walk to the beach through landscaped grounds. Good value for couples who want resort amenities without the luxury price tag. 2,000-3,500 THB ($57-100) per night.

• La Flora Khao Lak — Beachfront resort with infinity pool and direct sand access. Close to Tab Lamu Pier for early-morning boat departures. Sea-view rooms, attentive service, and a spa. The top mid-range choice for Similan visitors. 3,000-6,000 THB ($85-170) per night.

• JW Marriott Khao Lak — Sprawling luxury compound with multiple pools, a kilometer of private beach, and an on-site turtle conservation program. The breakfast buffet alone justifies a night. 7,000-15,000 THB ($200-425) per night. Where Khao Lak proves it can compete with Phuket’s best at a fraction of the crowd density.

The Islands After the Boats Leave

I stayed one night on Koh Miang in a national park bungalow, and the difference between the daytime Similans and the evening Similans is another destination entirely. By 4 PM the last speedboat has departed and the island belongs to the park rangers, a handful of campers, and the land crabs that emerge from the forest in staggering numbers after dark. I walked the beach at sunset — the water still and luminous, the granite boulders casting long shadows across sand that hundreds of feet had crossed that afternoon — and did not see another person for forty minutes. At dawn the next morning I snorkeled the house reef alone, floating over coral that had no other audience, watching a sea turtle surface to breathe three meters from my face. Those hours before the first speedboat arrives are the Similans as they were meant to be experienced — quiet, unhurried, and overwhelmingly alive.

For the broader Andaman coast experience, combine a Similan trip with time in Khao Lak for Khao Sok National Park access, or head south to Phuket and Krabi for different underwater landscapes. Our snorkeling guide ranks the Similans among the best sites in Thailand.