Off the Andaman coast, 65 km from mainland Thailand, the Similan archipelago lines up nine granite islands set against turquoise waters. Designated as Mu Ko Similan marine national park since 1982, this chain of islets ranks among Southeast Asia's premier diving destinations, with rich marine fauna and strict regulations to protect the coral seabeds.

At a glance

• Location: Andaman Sea, southern Thailand, 65 km offshore (Phang Nga province)
• Access: speedboat from Thap Lamu Pier, 15 km from Khao Lak (1h15 crossing)
• Season: open November to mid-May, closed during monsoon
• Prices: day excursion 3,000 baht (≈ €84) + park entry 400 baht
• Top activities: scuba diving, snorkeling, liveaboard cruise, sea turtle spotting
• Ideal duration: 1 day for beaches, 3 to 5 days for diving cruise
• Audience: divers (all levels depending on site), snorkelers, nature travelers

Why visit the Similan Islands

The Similans have drawn international divers since the 1980s for one simple reason: visibility regularly reaches 30 meters, and the diversity of underwater relief—granite drop-offs, coral gardens, tunnels, canyons—concentrates dense marine life within a compact area. Skin Diver magazine ranks the archipelago among the world's ten best diving sites.

Beyond the seabeds, the islands offer white-sand beaches edged by characteristic granite blocks, water at 28°C year-round, and preserved tropical vegetation. Since the park's reopening in October 2018, visitor numbers are capped at 3,850 per day, which transforms the experience compared to other saturated Thai archipelagos.

History and identity

Its name derives from the Yawi word "sembilan," meaning "nine," matching the number of islets. Yawi is the Malay language spoken by communities in southern Thailand, a legacy of historical ties between the Malay Peninsula and the Andaman coast.

Tourism on the Similan Islands developed in the early 19th century, and today the place is victim to its own success. Authorities' desire to manage mass tourism impacts and protect marine biodiversity prompted forestry authorities to adopt a new management plan. After reopening in October 2018, the park now receives only 3,850 tourists daily. Islands 1, 2, and 3 are now off-limits to landing to protect sea turtle nesting sites.

The archipelago shares its ecosystem with the Moken people, the "sea gypsies," who have navigated the Andaman Sea for centuries. You're more likely to encounter their villages on the neighboring Surin Islands to the north.

What to do and see

The archipelago reveals itself island by island, each numbered from south to north for easy navigation. The marine park has over twenty diving sites spread across the entire chain.

Island No. 1: Koh Hu Yong

At the archipelago's far south, Koh Hu Yong is known for its deserted beaches where sea turtles come to nest. Landing is now prohibited, but surrounding waters suit diving and snorkeling, with multicolored corals and visibility between 20 and 40 meters.

Island No. 2: Koh Pa Yang, realm of rays and sharks

Two major sites surround this island:

Sharkfin Reef — Southwest of the island, this site harbors pelagic sharks (hence its name) and large rays. Depth 18 to 40 m, visibility 10 to 30 m. Reserved for experienced divers.

Boulder City — Nearby, the site stands out for three emergent rocky peaks. Visibility is excellent between 12 and 30 m, but currents can be strong. Advanced level required.

Island No. 3: Koh Pa Yan

A small intermediate island, Koh Pa Yan is now closed to landing to protect its fauna. Boats pass offshore to reach the following sites.

Island No. 4: Koh Miang

The archipelago's second-largest island, Koh Miang is the only place where you can stay within the park. Its two adjoining beaches and forest trail make it the most convenient base for spreading visits. Bungalows and camping pitches are booked through the national park office.

Bird Rock, nearby, offers a network of tunnels, caves, and deep canyons populated with small fish. Visibility 15 to 40 m, generally weak currents but temperamental tides: caution for beginners.

Island No. 5: Koh Ha and Koh Hok, the twin islands

East of Koh Miang, these two twin islands offer rich marine fauna in accessible conditions. Currents are rare and weak, visibility excellent from 10 to 15 meters. Experienced divers can descend to 40 meters.

Island No. 6: Koh Payu

A medium-sized island at the archipelago's heart. Its large coral barrier, named The Garden Orchid, harbors a strong population of soft corals (red gorgonians, vinegar corals).

The East of Eden site, ranked among the country's best diving spots, is located here. You observe parrotfish, fusilier, frogfish, leopard shark, blacktip reef shark, grouper, and manta ray. Weak currents allow all levels. Night diving is recommended for seasoned divers: marine fauna is more active then.

Island No. 7: Koh Pa Boo

A small islet whose shallow turquoise waters make it ideal for snorkeling. Boats make a brief stop here before continuing toward the main islands.

Island No. 8: Koh Similan

The archipelago's largest island, which gave it its name. White-sand beaches, massive granite blocks, and crystalline waters sum up the postcard image of the Similans. Activities range from swimming to hiking up to the Sail Rock viewpoint.

On the diving side, three renowned sites encircle the island: Fantasea Reef, Beacon Point, and Elephant Head Rock. The latter, an underwater granite formation shaped like an elephant's head, is one of the Similans' signature sites, rather reserved for intermediate and advanced divers.

Island No. 9: Koh Ba Ngu

At the far north, Koh Ba Ngu is locally nicknamed "the snake island." The flagship site, Christmas Point, is found to the northwest: underwater galleries, rock formations, gorgonians, and sea anemones. You encounter barracuda schools, Napoleon wrasse, blacktip reef sharks, and frogfish.

When to go

The Similan Islands are open to visitors from November to mid-May. This regulation protects biodiversity: tourism activity would disrupt sea turtle nesting and reproduction. From May to October, monsoon makes the sea impassable and the park remains closed.

Within the Andaman dry season, each month has its logic:

• November: reopening, sea still choppy some days, moderate crowds
• December - January: high season, temperatures 26 to 30°C, calm seas, book ahead
• February: stable conditions, good compromise between crowds and weather
• March: maximum underwater visibility (up to 40 m), divers' reference month
• April: warmest waters (29-30°C), possible passages of manta rays and whale sharks
• Mid-May: gradual closure, first monsoon rains

How to get there

From Khao Lak (simplest)

The Thap Lamu Pier landing, 15 km south of Khao Lak, is the main departure point. The speedboat takes approximately 1h15 to reach the archipelago. Expect 3,000 baht (≈ €84) per person for a day excursion including transport, lunch, and snorkeling equipment.

From Phuket

Many agencies offer excursions from Phuket with road transfer included to Thap Lamu (approximately 1h30 drive, then the speedboat). The full day lasts 12 to 14 hours, making the option tiring: if possible, favor a night in Khao Lak the day before.

By liveaboard cruise

For serious diving, the cruise formula (3 to 5 days) is most suitable. You sleep aboard, dive 3 to 4 times daily, and access remote sites (Koh Bon, Koh Tachai, Richelieu Rock toward the Surin Islands). Prices start from €600 for 3 days.

Where to stay

Accommodation on the archipelago itself is strictly regulated: only Koh Miang island has bungalows and camping pitches managed by the national park office. Spartan comfort (fan, cold shower, limited evening electricity), but a night's stay on-site is worth it to escape the daytime crowds.

Most travelers stay in Khao Lak, the nearest mainland base, which covers all ranges:

• Guesthouses (€15-30): simple rooms along main roads or in back alleys of Nang Thong Beach, fan or AC, family welcome
• Boutique hotels (€60-120): human-scale beach resorts, pool, breakfast included, possible shuttle to Thap Lamu
• High-end lodges (€150+): beachfront resorts with spa, fine-dining restaurant, and private Similan excursion arrangements

For a liveaboard cruise, accommodation is included in the voyage price.

Practical tips

• Book early: the daily 3,850-visitor cap is regularly reached in high season (December-February)
• Reef-safe sunscreen mandatory: sunscreens containing oxybenzone and octinoxate are banned in the park
• National park permit: the 400-baht entry fee is paid directly at the pier or included in the excursion; keep your ticket
• Water and snacks: standard excursions provide lunch, but bring a reusable water bottle (plastic bottles are discouraged)
• Seasickness: the speedboat crossing is bumpy; take a tablet 30 minutes before boarding if prone to it
• Cash: no ATM on the islands; bring cash for extras at Koh Miang

Insider tips

A few notes that regular visitors to the area share:

• If you don't dive, a day at Koh Miang + Koh Similan (islands 4 and 8) more than suffices and avoids fatigue from chaining short stops
• To photograph Sail Rock on Koh Similan without crowds, climb to the viewpoint when the first boat arrives, around 9:30am
• March remains the prime month for visibility, but April offers the best chances to spot a manta ray or whale shark
• Liveaboards combining Similan + Surin (with Richelieu Rock) are the most comprehensive; they often book six months ahead
• Favor operators landing mid-afternoon on Koh Similan: the light is better and morning boats have departed

For whom?

• Advanced divers: the archipelago is a major world destination, best experienced via a 3 to 5-day liveaboard cruise
• Beginner divers: feasible on a day excursion at accessible sites (Koh Miang, Koh Ha)
• Snorkelers and swimmers: Koh Pa Boo, Koh Miang, and Koh Similan offer shallow waters and fine beaches
• Families: day trip possible if children tolerate the speedboat; otherwise prefer Phi Phi or Koh Yao Yai islands, closer
• Nature photographers: favor a night on Koh Miang for morning and evening light
• Travelers seeking calm: the archipelago is crowded by day; silence returns only after boats depart around 4pm

Also discover

The Similans naturally combine with other Andaman coast destinations:

• Khao Lak, mainland base 67 km away, ideal for exploring the archipelago
• Ko Phra Thong, a wild and pristine island 88 km north
• Khura Buri district, departure point to the Surin Islands
• Khao Sok National Park, jungle and Cheow Lan Lake 115 km away
• Phang Nga Bay, its karst peaks and floating villages
• Koh Yao Noi Island and Koh Yao Yai, tranquil alternative between Phuket and Krabi