Similan Islands: Season, Rules and Snorkelling from Phuket

The Similan Islands are a protected marine national park in the Andaman Sea, about 60 to 70 kilometres off the coast of Phang Nga province, north of Phuket. They open only in the dry season, roughly from mid-October to mid-May, and a day trip from Phuket starts very early and returns in the evening. In exchange you get some of the clearest water and whitest sand in Thailand.

When is the Similan National Park open?

The park closes every year for the southwest monsoon, when the sea is too rough for small boats and the reefs are given time to recover. As of 2026 the usual season runs from about 15 October to 15 May, but the exact dates are set by the national park authorities each year and can shift. Never book a trip in the closed season, whatever a street vendor promises.

Period	Conditions	Our view
Mid-October to November	Park newly open, sea can still be choppy, fewer visitors	Good value, but keep a spare day in case of cancellations
December to February	Calmest sea, best visibility, peak season	The best time; book early
March to April	Hot, calm, often excellent visibility; plankton can bring manta sightings for divers	Very good, slightly fewer crowds after Easter
Early to mid-May	Weather starting to change before closure	Possible, but higher chance of rough crossings
Mid-May to mid-October	Park closed	No trips

How the day trip from Phuket works

Boats to the Similans do not leave from Phuket itself. They depart from piers on the Khao Lak coast in Phang Nga, mainly Thap Lamu. That means a road transfer from your Phuket hotel first, usually around one and a half to two hours depending on where you stay, then roughly an hour to an hour and a half by speedboat to the islands.

A typical day looks like this:

1. Very early pickup from your hotel, often between 6 and 7 a.m.
2. Pier briefing with breakfast and fitting of snorkel gear and life jackets.
3. Speedboat crossing to the park.
4. Two or three snorkelling stops at different islands and reefs.
5. Beach time and lunch, usually on Koh 4 (Koh Miang) or Koh 8 (Koh Similan).
6. Return crossing in the afternoon and drive back to Phuket in the evening.

Our early Similan Islands speedboat trip from Phuket with snorkelling follows this pattern and runs about twelve hours door to door. Leaving early matters: you reach the first reef before the bulk of the day boats, when the water is calmer and the beaches emptier.

What you will see

Islands and beaches

The park has nine main islands, numbered from south to north, plus Koh Bon and Koh Tachai further north (Koh Tachai has been closed in some recent seasons to protect it). The highlights on most day trips:

• Koh 8 (Koh Similan): the largest island, with Donald Duck Bay and the famous granite boulder known as Sail Rock. A short but steep path leads to a viewpoint over the bay; wear proper shoes rather than flip-flops.
• Koh 4 (Koh Miang): home of the park headquarters and a long, gentle beach. Often the lunch stop.
• Koh 9 (Koh Ba Ngu): the "snake head" island, with good snorkelling in the bays.

Snorkelling

Visibility in the high season often reaches 20 to 30 metres, which is much clearer than the bays around Phuket. Expect hard and soft corals, parrotfish, clownfish in anemones, large schools of fusiliers and, quite often, turtles. Reef sharks are sometimes seen by divers on the deeper sites. The coral took a heavy hit from warm-water bleaching events, so not every reef is in perfect condition, but recovery since the park started limiting numbers has been visible.

If you are not a strong swimmer, wear the life jacket. You can still see a great deal floating on the surface, and the crew will usually choose a sheltered side of the island when the current is strong.

Park rules you should know

The Similans are strictly managed. As of 2026 the main rules include:

• A daily cap on visitors, which is why trips in peak season sell out.
• A national park entrance fee for foreign visitors, collected per person. On many trips it is paid separately at the pier; check what your booking includes.
• No touching or standing on coral, and no collecting shells, sand or coral.
• No feeding fish.
• No single-use plastic brought onto the islands, and sunscreen containing certain chemicals harmful to coral is banned. Use a reef-safe mineral sunscreen or, better, a rash vest.
• No smoking on the beaches.

Fines for breaking these rules can be substantial, and park rangers do enforce them.

Similans or Phi Phi?

Both are classic day trips from Phuket, but they suit different people. Phi Phi is closer, livelier and famous for Maya Bay and its dramatic cliffs; the scenery is the point. The Similans are further, quieter and all about the water: snorkelling, visibility and white sand. If you have time for only one and snorkelling is your priority, choose the Similans in season. If you want viewpoints, lagoons and a more social atmosphere, Phi Phi is the better day.

Practical tips

• Seasickness: the speedboat crossing can be bumpy. Take a tablet before you leave the pier, sit towards the back, and eat a light breakfast.
• What to bring: swimwear, a rash vest, reef-safe sunscreen, a hat, a towel, a dry bag for your phone, cash for the park fee if needed, and closed shoes for the Sail Rock path.
• Your own mask: boats provide gear, but a mask that fits you well makes a real difference.
• Staying in Khao Lak: if the Similans are a priority, staying a few nights in Khao Lak cuts the transfer to around fifteen to thirty minutes and makes the day much easier.
• Cancellations: trips are cancelled when the sea is unsafe. Build your plan so the Similans are not on your last day.

Is it worth it?

For anyone who enjoys being in the water, yes. It is a long day and it is not cheap compared with a Phuket bay trip, but the clarity of the water and the quality of the beaches are on another level. For families with very young children or anyone who suffers badly from seasickness, a calmer trip such as Phang Nga Bay may be a better choice.

FAQ

When do the Similan Islands open?

Usually around 15 October each year, closing around 15 May. The exact dates are announced by the national park authorities and can change, so check before you book.

How long is the trip from Phuket to the Similan Islands?

Allow about two hours by road to the pier at Khao Lak, plus around an hour to an hour and a half by speedboat. A full day trip is typically eleven to twelve hours.

Can you stay overnight on the Similan Islands?

Overnight stays on the islands have been restricted in recent seasons. Divers who want more time usually join a liveaboard boat departing from Khao Lak.

Can non-swimmers go to the Similans?

Yes. With a life jacket you can float and snorkel at the surface, and the beaches are lovely on their own. Tell the crew so they can keep an eye on you.

Is Similan snorkelling suitable for children?

Confident swimmers from about eight years old usually enjoy it. The long day and the open-sea crossing are the harder parts for younger children.