Similan Islands, Thailand: Diving, Best Season and How to Visit

Similan Islands at a glance

Across the Thailand trips we plan, most travellers add the Similans as a diving day out or a liveaboard from a Khao Lak or Phuket base, usually inside a wider 5 to 7 day trip.

Is Similan open right now?

Right now, in August, no. Mu Ko Similan National Park runs on a fixed seasonal calendar. It closes to all visitors on 16 May and stays shut through the southwest monsoon until 14 October, then reopens for the dry season from about 15 October to 15 May. The 2025 to 2026 season ran 15 October 2025 to 15 May 2026, and the park is expected to reopen for the new season around 15 October 2026. This closure is enforced, not advisory. Boats are not allowed to land during the monsoon, so there is no way to visit outside the window. If you are planning ahead, put your dates anywhere between late October and early May.

When is the best time to visit the Similan Islands?

The short version: come between November and April, and pick February or March if you can. The sea is calmest and visibility is at its best in those two months, often 20 to 30 metres, which is why underwater photographers plan their year around them. February to April is also the window for the big animals. Whale sharks and manta rays move through the northern sites like Koh Bon and Richelieu Rock in this period. Early season (late October and November) brings warming water and thinner crowds, while March and April have the warmest water and the busiest boats. The park then closes from mid-May, so there is no late-season option.

How do you get to the Similan Islands?

You cannot base yourself on Phuket and hop over casually. The Similans lie about 84 km northwest of Phuket, and every trip runs by boat from the mainland during the open season. Most speedboats leave from Thap Lamu pier near Khao Lak, the closest launch point, on a crossing of roughly 60 to 90 minutes. If you are staying in Phuket, day-trip operators collect you from your hotel, drive about 90 minutes north to Thap Lamu, and put you on the same boats, so plan for a long day either way. There is no airport on the islands and no public ferry you board on your own. You go with a licensed day-trip or liveaboard operator. For the full breakdown of piers, transfer times and operators, see our guide on how to reach the Similan Islands.

Diving and liveaboards in the Similan Islands

This is why most people come. The Similans are consistently ranked among the world's best dive destinations, so it is worth getting specific. You have two ways to dive here: a day trip or a liveaboard.

A day trip runs three dives at the southern and central reefs and gets you back to Khao Lak by evening. Budget about USD 80 to 120 (roughly Rs 6,600 to Rs 10,000) for a certified diver, less for snorkellers. A liveaboard is the real Similan experience. You sleep aboard for three to six days, reach the northern sites that day trips cannot, and wake up on the dive site. Expect from about USD 900 (roughly Rs 75,000 and up) for a four-day trip with all meals and dives included.

The sites themselves are the draw, and this is where the Similans pull ahead of every other reef in Thailand:

• Richelieu Rock: a horseshoe-shaped pinnacle north of the main islands, the region's signature site and the best spot in Thailand for whale sharks and seahorses.

• Elephant Head Rock (Hin Pusar): a maze of granite boulders and swim-throughs off Island 7, the most photographed dive in the park.

• Christmas Point: dramatic boulder swim-throughs and soft coral at the northern tip near Island 9.

• Boulder City: a sloping ridge of giant granite boulders, good for drift dives and reef sharks.

• East of Eden: a gentle coral garden off Island 7, superb for snorkellers and relaxed dives.

• Koh Bon and Koh Tachai: the northern manta and whale-shark cleaning stations, usually reached only on a liveaboard.

"Book the northern liveaboard route if you want Richelieu Rock and Koh Bon on the same trip, and aim for February or March for the mantas," says our Phuket dive-desk partner. Diving here needs a licensed operator, the park fee and, in high season, advance booking. If you would rather have it packaged with transfers and stay, our Thailand tour packages include liveaboard-friendly Similan diving itineraries.

The nine islands and what to do

Similan comes from the Malay word sembilan, meaning nine, and the park is built around nine main granite islands numbered south to north (Koh Hu Yong, Koh Payang, Koh Payan, Koh Miang, Koh Ha, Koh Payu, Koh Hin Pusar, Koh Similan and Koh Bangu), with two northern additions, Koh Bon and Koh Tachai, folded into the same marine park. You will not set foot on most of them. A handful are open to visitors, and these are the ones that matter:

• Koh Miang (Island 4): the park headquarters, with the ranger station, two beaches, the campsite and bungalows, and short jungle trails to viewpoints.

• Koh Similan (Island 8): the largest and most photographed island, home to Sail Rock at Donald Duck Bay and the boulder-top viewpoint that shows up on every postcard. Its main beach is a classic snorkelling stop.

• Koh Bangu (Island 9): the northernmost of the nine, largely a protected bird sanctuary, with Christmas Point just offshore.

Above water it is fine white beaches, short jungle walks and viewpoints; below it is the snorkelling and diving. Between dives, the Donald Duck Bay viewpoint on Island 8 and the pale sand of Koh Miang are the two things almost everyone does. Wildlife on the islands includes crab-eating monkeys, squirrels, langurs, lizards, fruit bats and a wide range of birds, with ironwood and gum trees, jackfruit, rattan and bamboo across the forested interiors.

Entry fees and park rules

Every visitor pays the national park entrance fee, and it is collected on top of your tour price. For foreign visitors it is 500 THB for adults and 250 THB for children aged 3 to 14; Thai nationals pay 100 THB and 50 THB. The park is open 08:00 to 16:00 during the season. A few rules are enforced strictly and worth knowing before you go. Single-use plastics are banned and will be taken at the pier, you must use reef-safe sunscreen, and standing on or touching coral carries fines. Drones need prior permission. The fees and season dates here are checked by our Thailand desk against the Department of National Parks notices for Mu Ko Similan. For the current fee breakdown and what it covers, see our Similan Island entry fees page.

Where to stay

Accommodation on the islands themselves is deliberately limited. There are no resorts or proper hotels inside the park. Your only on-island options are the national park bungalows and the campsite on Koh Miang (Island 4), and there are very few of them, around 35 rooms in total, so they sell out weeks ahead in high season and must be reserved through the park in advance. Most travellers skip that and base themselves in Khao Lak, the closest mainland town, which runs from budget guesthouses to beach resorts and sits 60 to 90 minutes from the pier. Phuket works too if you do not mind the longer transfer. Divers who want to maximise water time choose the third route and simply live aboard the boat. For specific hotels and areas, see our guide to hotels in and around the Similan Islands.

Are the Similan Islands worth it?

For the diving and snorkelling, yes, comfortably. Few places in Thailand combine granite-boulder scenery, healthy coral and a real chance of whale sharks in one trip. The caveats are honest ones. It is a long day out from Phuket, the park is closed for half the year, and on peak-season mornings the main beaches see a lot of day-trippers at once. Go early in the day, or go by liveaboard, and you sidestep most of the crowd. If you have time for one marine excursion from Phuket or Khao Lak and you care about what is under the water, the Similans are the one to pick. Planning a wider trip? Our Thailand travel guide and Similan Islands overview help you slot it into a Phuket or Khao Lak itinerary.