Similan Islands from Khao Lak

The Similan Islands are the best-known island group in Thailand's Andaman Sea and the most popular day trip from Khao Lak. White sand, huge granite boulders, remarkably clear water and some of the country's best snorkelling make the Mu Ko Similan National Park a highlight of any stay on this coast.

This guide covers what you need to know before you go: when the park is open, which islands you can visit, what a typical day trip looks like, how to choose between a speedboat and a speed catamaran, and what to bring.

What are the Similan Islands?

The name comes from the Malay word for "nine". The original group was nine islands, numbered from south to north. Ko Bon and Ko Tachai were later added to the Mu Ko Similan National Park, so the protected area now covers eleven islands.

Above water the islands are all bright beaches, thick tropical forest and striking granite formations. Below it are coral reefs, boulder fields and a wide range of habitats for tropical fish and other marine life.

When can you visit?

The national park is normally open from 15 October to 15 May and closed to tourists from 16 May to 14 October. The season falls mostly in the drier months on the Andaman coast, when the sea is usually calmer than during the south-west monsoon – but wind, waves and visibility are never guaranteed.

The seasonal closure limits visitor numbers, keeps boats off the water during the roughest months and gives the reefs time to recover. The exact opening and closing dates are set by the park authorities each year.

There is no longer any accommodation on the islands. The old bungalows and campsite are no longer part of normal visitor operations, so the Similans can only be visited on a day trip. Hotels are on the mainland, mainly around Khao Lak.

Which islands do you visit?

Not every island in the park can be visited. Where your boat stops depends on the approved route, the weather, sea conditions and the park's current rules. The two main visitor areas are:

Ko Tachai belongs to the national park but remains closed to normal landings. Protected areas and permitted activities can also change during the season.

A typical day trip from Khao Lak

Almost everyone visits the Similans on an organised day trip. The day starts early:

1. Early pick-up from your hotel in Khao Lak
2. Check-in, breakfast or a snack and a safety briefing at the pier, usually Thap Lamu
3. About an hour and a half by speedboat or speed catamaran to the national park
4. Several beach, viewpoint and snorkelling stops
5. Lunch in an approved visitor area
6. Return to the mainland in the afternoon and transfer back to your hotel

Most trips include hotel transfers, food and drinks, an English-speaking guide, mask and snorkel, fins or reef shoes, life jackets and basic accident insurance. Towels, the national park fee and photos are not always included. The route varies between operators and can change on the day if the weather, currents or park rangers require it.

Speedboat or speed catamaran?

Choosing the boat is one of the biggest decisions. Both get you to the islands, but they feel different on the water and often carry different group sizes.

Classic speedboat

Speedboats have been the standard for Similan trips for years. They're fast, nimble and offered by lots of operators, so there's plenty of choice on price. A speedboat is a good pick if you want a tried-and-tested trip and don't mind a livelier ride.

In choppy seas the crossing can be bumpy, though. If you have back problems, a sensitive stomach or are prone to seasickness, bear that in mind.

Speed catamaran

A speed catamaran has two hulls and usually more room than a standard speedboat. Most people find the ride steadier and more comfortable – although a catamaran still depends on the sea on the day. It's worth a look for families, anyone who wants more space, or anyone who feels uneasy on smaller boats.

A bigger boat doesn't automatically mean a smaller group, so check the maximum number of passengers too.

What to check before you book

• Departure from Khao Lak. Booking sites often mix trips from Phuket and Khao Lak. If you're staying in Khao Lak, pick a trip that leaves from Thap Lamu or includes pick-up from your hotel – travelling via Phuket wastes half a day. Hotels further out, such as Natai, Khok Kloi or well north of Khao Lak, may cost extra to collect.
• National park fee. Some trips include it, others ask for cash on the day. Check whether it's included and whether children pay a reduced rate.
• Boat type. Don't rely on the main photo or the title – read the description, and ask which boat runs on your date if in doubt.
• Group size. "Premium" doesn't necessarily mean small group. Look for a stated maximum number of guests.
• Time in the water. Keen snorkellers should look at how long each stop is rather than how many islands are listed. Two good long snorkel stops beat a rushed programme.

Snorkelling

For most visitors the clear water is the main reason to go. Depending on the spot you can see coral, shoals of fish, anemone fish and many other tropical species. Visibility changes from day to day: wind, currents and waves can stir the water up. Even strong swimmers should follow the crew's instructions and stay within the marked snorkelling areas.

Diving

The waters around the Similans are among Thailand's best-known dive areas, with coral reefs, granite boulders, swim-throughs and drop-offs at a range of depths. Diving is a different trip from a snorkelling day tour, though: dive boats plan around your experience, certification, the weather and which sites are open. Ask one of Khao Lak's dive centres about day trips or liveaboards.

Protecting the islands

The Similans aren't an ordinary beach destination but a fragile protected area. The annual closure, limited visitor areas and controlled boat traffic are all there to protect the islands and reefs. Even in season individual bays, dive sites or parts of the islands may be closed – that's not a flaw in your trip, it's part of running a national park responsibly.

The best visit leaves as little trace as possible: take nothing, leave nothing and watch the wildlife from a distance.

Don't take sand, shells or coral home with you.

What to bring

• Sun cream (reef-friendly), hat and sunglasses
• Swimwear and a dry change of clothes
• Towel and a small waterproof bag
• Seasickness tablets if you need them
• A refillable water bottle, if allowed
• Your passport or a copy of it, if the operator asks

Who is the trip suitable for?

A Similan trip suits anyone who wants to combine nature, beaches and snorkelling – but it's an early start, a long boat ride and an active day, with climbing in and out of the boat. For families with young children the early pick-up, sun and several stops can be tiring, so check the minimum age, life jackets and the day's schedule.

Speedboat trips are generally not recommended during pregnancy or for people with back, neck or joint problems or serious heart conditions. Read the operator's conditions before booking and ask your doctor if in doubt.

Similan Islands tours from Khao Lak

These aren't a complete ranking – they show the different types of trip you can compare. Prices, availability, inclusions and boats change, so always check the details for your date.

Affiliate note: some links on this page are affiliate links. If you book through them, Khao Lak Wired may earn a small commission at no extra cost to you. It doesn't affect which tours we mention.

Frequently asked questions

When are the Similan Islands open?

The normal season runs from 15 October to 15 May. Between 16 May and 14 October the national park is closed to tourists.

Can you stay overnight on the islands?

No. Overnight stays are not currently allowed, so the islands can only be visited on a day trip.

Can you visit independently?

Access is by boat and subject to national park rules. For almost everyone, an approved organised boat trip is the practical way to go.

Is every trip good for snorkelling?

Most day trips include snorkelling stops, but conditions depend on the weather, currents, visibility and the approved route on the day.

Are the Similans suitable for children?

That depends on their age, how well they swim and how they cope with a long speedboat ride. Ask the operator about minimum age, children's life jackets and the schedule.

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