Similan Islands Day Trip Guide 2026–27: The Season Opens 15 October

Every year on 15 October, park rangers untie the mooring lines, the speedboats line up at Thap Lamu pier, and the Similan Islands open for a new season. If you are in Phuket between mid-October and mid-May, a Similan day trip is one of the best things you can do with a single day: some of the clearest water in Thailand, granite boulders the size of houses, and reefs where turtles and clownfish are a normal sighting rather than a lucky one. This guide explains how the day actually runs, what to expect at each island, the rules you need to know, and how to choose between our two Similan tours.

When is the Similan Islands season in 2026–27?

Mu Ko Similan National Park opens on 15 October and closes on 15 May. The closure covers the south-west monsoon, when swells make the open-sea crossing unsafe and the reefs get a five-month rest. For the 2026–27 season that means the first trips run on 15 October 2026 and the last ones on 15 May 2027.

Within the season, conditions change month by month:

• Mid-October to November: the islands are freshly reopened and the reefs are at their quietest. The tail of the rainy season can still bring a choppy crossing or a cancelled day, so keep a buffer in your plans.
• December to March: the classic window. Calm seas, sunshine and the best visibility, often 20 metres or more on a good day. Also the busiest months, especially around Christmas, New Year and Chinese New Year.
• April to mid-May: hot, mostly calm and slightly less crowded. Late-season plankton can reduce visibility at times, but it also brings bigger marine life to the dive sites further out.

If you are still deciding when to travel, our month-by-month guide to Phuket’s weather and sea conditions shows which islands work best in which months.

Where exactly are the Similans, and how long is the day?

The Similans sit in the Andaman Sea off the coast of Phang Nga province, north-west of Phuket. The park was created in 1982 around nine islands (the name comes from the Malay word sembilan, “nine”); Koh Bon and Koh Tachai were added later. The islands are numbered from south to north, which is why guides talk about “Island 4” or “Island 8”.

Boats do not leave from Phuket itself. Day trips depart from Thap Lamu pier near Khao Lak, so the day starts early. Here is a realistic timeline based on our tours:

Time	What happens
05:30–07:30	Hotel pickup in Phuket (earlier for Patong, Kata and Karon; later if you stay in Khao Lak)
07:00–08:00	Check-in at Thap Lamu, light breakfast, safety and coral-care briefing
Around 09:00	Speedboat departs; the crossing takes roughly 1 hour 15 minutes
10:15–15:15	Island stops, two snorkelling sessions, beach time and lunch
16:30–17:30	Back at the pier, then the van ride to your hotel

It is a long day, around 11 to 12 hours door to door from Phuket. Most guests sleep in the van on the way back, and almost all of them tell us it was worth it.

What will you see on a Similan day trip?

Island No. 8 (Koh Similan): Sail Rock and Donald Duck Bay

This is the postcard. A short but steep scramble over rocks and wooden steps takes you up beside Sail Rock, the balanced granite boulder that overlooks Donald Duck Bay. The view of the curved white beach and two shades of turquoise below is the photo everyone wants. Wear sandals with a strap or water shoes, not flip-flops, and take your time on the way down. If you would rather not climb, the beach below is soft, sheltered and good for swimming.

Island No. 9 (Koh Ba Ngu): reef snorkelling

Ba Ngu is the northern end of the main chain and a regular first snorkelling stop. The boat moors at a buoy and you snorkel straight from the deck over hard and soft corals, with parrotfish, butterflyfish, anemones and the occasional blue-spotted stingray resting on the sand.

Island No. 7 (Koh Payu): turtles and clownfish

On our Similan Islands tour with Sail Rock views, the afternoon snorkel is at Koh Payu, where green and hawksbill turtles are often seen grazing and clownfish shelter in large anemones. Nobody can promise wildlife, but turtle sightings here are common enough that guides keep a running tally.

Island No. 4 (Koh Miang): Honeymoon Bay and Princess Bay

Koh Miang is home to the park headquarters and two of the prettiest small beaches in the group. It is a calm place for a swim after lunch, and you may spot the large Nicobar pigeons and monitor lizards that live in the forest behind the beach.

Which Similan tour should you choose?

We offer two Similan day trips, both run by experienced local operators out of Thap Lamu. They cover the same famous islands but are built a little differently.

	Similan Islands Day Tour	Similan Islands Tour with Sail Rock Views
Price	From ฿4,300 per adult	From ฿3,600 per adult
Main stops	Koh Miang (No. 4), Ba Ngu (No. 9), Similan Island (No. 8)	Donald Duck Bay and Sail Rock (No. 8), Ba Ngu (No. 9), Koh Miang (No. 4), Koh Payu (No. 7)
Snorkelling	From the boat at Miang and Ba Ngu	Coral Bay at Ba Ngu and turtle spot at Koh Payu
Food	Light breakfast at the pier, beachside lunch, fruit and snacks	Light breakfast at the pier, Thai lunch on the island, fruit and snacks
Best for	A relaxed pace with more beach time	Keen snorkellers who want the turtle stop

Both include snorkelling gear, drinks, travel insurance, an English-speaking guide and a toilet on board. The Similan Islands Day Tour suits families and first-timers who want a gentler rhythm; the Sail Rock tour packs in one more snorkelling site. Neither is a bad choice. If you cannot decide, tell us what matters most to you and we will point you to the right one.

What are the national park rules?

The Similans are a protected marine park, and rangers do enforce the rules. The ones that matter on a day trip:

• No standing on or touching coral, and no feeding fish. Your guide will show you where to enter and exit the water.
• Reef-safe sunscreen only. Products containing oxybenzone, octinoxate, 4-methylbenzylidene camphor (4-MBC) or butylparaben are banned in Thai marine parks, with fines of up to 100,000 baht.
• Take nothing away: no shells, sand, coral or plants.
• No littering, and keep single-use plastic to a minimum.
• Park entrance fee: foreign visitors pay a national park fee (at the time of writing around ฿500 per adult and less for children). Check your booking to see whether it is included or paid in cash on the day.

Koh Tachai, further north, has been closed to tourists since 2016 so its reef and beach could recover. A reopening has been discussed but not confirmed, so no day tour currently includes it.

Is a Similan trip right for you? Fitness, kids and seasickness

You do not need to be a strong swimmer. Life jackets are provided and you can snorkel while wearing one. You do need to be comfortable with an open-sea speedboat crossing of more than an hour each way, which can feel bumpy when the wind picks up.

• Not suitable for: pregnant travellers, people with back or spinal problems, heart conditions or other serious health issues, and anyone very prone to seasickness.
• Children: school-age children who enjoy the water usually love it. For toddlers, the early start and long boat ride are a lot to ask. Racha Island is a gentler alternative (see our family day trip guide).
• Seasickness: take a tablet 30–60 minutes before boarding, sit towards the back of the boat, and keep your eyes on the horizon.

What should you bring?

Swimwear (wear it under your clothes), reef-safe sunscreen, a hat, sunglasses, a towel, a light long-sleeved top or rash guard, water shoes for the Sail Rock climb, a dry bag for your phone, and some cash. Bring your passport or a clear copy too, because operators need passport details for the national park. Our full island day trip packing checklist covers the rest.

Booking tips for opening season

• Book a few days ahead in December–February. Boats fill up, and the park limits daily visitor numbers.
• Plan the Similans early in your stay. If weather cancels your date, you will still have time to reschedule.
• Booking with us costs nothing up front. Your card is only charged once the local operator confirms availability, and you can cancel free of charge up to 72 hours before the trip.

If snorkelling is the main reason you’re coming, also read our guide to the best snorkelling spots around Phuket, which compares the Similans with Surin, Racha and Phi Phi.

The season is short, and the good dates go first. Have a look at our Similan Islands Day Tour and the Sail Rock and turtle snorkelling tour. If you want a private boat or a combined Similan–Surin plan, message our team and we will help you put it together.