The Similan Islands Travel Guide

The Similans are not a place you stay. They are a national park of nine uninhabited granite islands in the open Andaman, sixty kilometres west of the Phang Nga coast, with no hotels, no roads and no permanent population. Every visit begins on the mainland and ends there, the same day or after a few nights on a boat.

They are also, by most accounts, the best diving in Thailand, and the best sand: granite boulder formations on the west side of the chain, coral gardens on the east, water clear enough that the day boats anchor over reef you can see from the deck.

And they are shut for about half the year. That is the first thing to understand about them, and it is the thing this page can tell you something new about.

The closure is not a whim, and here is what it tracks

Every page about the Similans reports the closure as a pair of dates. Almost none of them says why the dates are there, and the reason is the reason the whole trip works or does not.

Three things fall out of that table.

The park is shut for exactly the months when the sea doubles. Across the six closed months the wave height at Koh Similan averages 1.36 metres; across the six open ones, 0.68. That is not a coincidence of the calendar. These are small islands in open ocean with nothing to windward, and the southwest monsoon turns a ninety-minute speedboat crossing from a boat ride into an ordeal.

The sea at the pier tells you nothing. Nang Thong beach at Khao Lak, where the boats leave from, runs at less than six-tenths of the Similan figure in every single month. Standing on flat sand at eight in the morning is not evidence about the water you will be in at half past nine.

October is not February. The park reopens around mid-October while the sea is still coming down: October averages 1.01 metres against February’s 0.66. An early-season trip is cheaper and it is a rougher crossing, and both of those are true at once.

None of this predicts the dates. The park authority sets them each season and they move by weeks, sometimes announced late. If your flights depend on the Similans being open, check the current season directly rather than trusting any page including this one.

Day trip or liveaboard

There are two ways to do this and they are barely the same activity.

A day trip is a long day. An early pickup, an hour and a half to two hours each way in a speedboat, three or four stops, and back on the mainland by late afternoon. It is the affordable way and it is how most people see the islands, divers and snorkellers together on the same boat. In any swell it is uncomfortable, and the swell is the thing the table above is about.

A liveaboard of two to five nights is what the Similans have their reputation for. It is the only way to reach the northern sites, to dive the good ones at the right time of day, and to be at the islands when the day boats are not. It is also, for a certain kind of diver, the point of coming to Thailand at all.

The diving page sets out the sites, what a liveaboard actually costs you in time, and where Richelieu Rock fits.

Snorkelling, and the beaches

Worth saying plainly, because a lot of pages imply otherwise: the Similans are excellent for snorkelling and a large share of day-trip passengers never put a tank on. The reef comes shallow, the water is clear, and the granite makes for better swimming than a flat reef flat does.

The sand is the other half of it. Koh Similan and Koh Miang have beaches that are white in the way photographs promise and rarely deliver, and it is coral rather than quartz: the white sand here is ground reef. It is also, in season, shared with several hundred other people who arrived on the same boats, which is the trade the day trip makes.

Visitor rules, and how much they change

The park caps daily numbers, restricts which islands you may land on, and ended most overnight stays some years ago. Rules here have moved several times in the past decade and consistently in one direction, towards fewer people and fewer places.

The practical consequence is that any specific claim about which island you will set foot on, or where you might sleep, is worth checking with an operator in the season you are travelling rather than reading off a page. We are not going to publish a list that is likely to be wrong by the time you use it.

The Surin Islands, and how they differ

Further north and on a similar calendar, the Surin Islands are the quieter alternative: better shallow snorkelling, less infrastructure, a fraction of the boats, and a Moken sea-nomad community on Koh Surin Tai. They are what the Similans were before the Similans became the thing everyone books.

They are the answer when the Similans are full rather than when the Similans are shut, because they close for the same monsoon and for much the same reason.

Getting there

Everything leaves from Thap Lamu pier, a few kilometres south of Khao Lak, whether you book in Khao Lak, in Phuket or online. That single fact settles most of the planning, and it is the reason a Phuket booking costs you two or three extra hours in a minibus for exactly the same boat.

Getting to the Similan Islands has the comparison from Khao Lak, Phuket and Krabi, and what each actually costs in time.

How long to give it

One long day if you are snorkelling, and build the rest of the trip around Khao Lak rather than around the islands. Three or four nights on a boat if you dive, in which case the boat is the holiday and the mainland is the airport.

Either way the season decides everything before you decide anything. The Khao Lak weather page sets out what the mainland does month by month, and the Andaman Coast guide covers which months work on this side of the country.