The Similan Islands
The park closes from 15 May to 15 October. Inside the season: granite boulder country, thirty-metre water, and a private boat out of Khao Lak.
Where
Phang Nga
Best time
November to April, inside the park season, with the clearest water usually in February and March.
The Similans are eleven granite islands some sixty kilometres off the Phang Nga coast, and they are the reason people base themselves at Khao Lak rather than Phuket. Granite is the distinction. Almost everything else in the Andaman is limestone, which crumbles and clouds the water; here the islands are heaps of rounded boulders the size of houses, above the water and below it.
The two sides of each island dive differently. The west faces are boulder country — swim-throughs, canyons, channels you thread — while the east sides shelve into hard and soft coral gardens in ten or fifteen metres. Visibility runs past thirty metres often enough that it stops being remarkable.
None of it is available for five months of the year, and that is deliberate.
When the Similan Islands close, and why
Mu Ko Similan National Park closes to visitors from 15 May to 15 October every year, and the Surin Islands to the north keep the same dates. The stated reason is the south-west monsoon — the crossing is genuinely rough and visibility collapses — but the closure has become a conservation instrument as much as a safety one, giving the reefs five months with nothing on them. Since 2018 overnight stays on the islands have ended and daily visitor numbers have been capped.
Plan accordingly. A February booking is a Similan trip; a June booking is not, and no amount of arrangement changes that. In the closed months we point people to the Gulf, which runs on the opposite monsoon and is at its best then.
What a day in the water actually looks like
The islands are numbered one to eleven from the south, and most of the diving happens around four, five, seven, eight and nine. Koh Similan itself, island eight, carries the sail-shaped boulder above Donald Duck Bay that appears on every poster of the place, and the short climb to it is worth doing between dives. At the northern end of the park lie Koh Bon and Koh Tachai, where the currents bring manta rays through in season.
A private day means three or four dives at a pace set by your party rather than a timetable, with surface intervals spent at anchor in a bay rather than motoring to the next fixture.
Snorkelling here, if you do not dive
The Similans work better for snorkellers than most dive destinations do, because the eastern reef flats sit in three to eight metres of water and the visibility means you read the deeper structure from the surface anyway. Turtles feed on the shallow flats, and the boulder fields drop away close enough to the beach that you can float over the edge of them.
What the surface does not give you is the swim-through architecture on the western sides, which is the argument for a try-dive if you have never breathed underwater. Either way the day is long: the crossing from Khao Lak takes the better part of two hours.
How We Visit
Our way in
We run the Similans privately from Khao Lak, which shortens the crossing and lets us leave before the day fleet. The boat is chartered for your party alone, with a dive guide to every two divers and a separate guide for snorkellers where the group is mixed, and the day is built around where the current is working rather than a fixed list of sites. We plan Similan days only inside the park season, and where your dates fall outside it we will say so at the outset rather than sell you something adjacent.
Questions
What travellers ask
When do the Similan Islands close?
The national park closes from 15 May to 15 October every year, reopening on 16 October. The Surin Islands to the north keep the same dates. The closure covers the south-west monsoon, when the crossing is rough and visibility poor, and it gives the reefs five months without visitors. There is no way to visit during it; if your dates fall inside the closure, the Gulf islands are the alternative.
Are the Similan Islands good for snorkelling as well as diving?
Yes. The eastern sides of the islands shelve into coral gardens in three to eight metres of water, shallow enough to snorkel and clear enough that you can see the deeper boulder fields from the surface. Turtles feed on the flats. What snorkelling misses is the swim-through architecture on the western sides, which is diving country. A mixed party works well on a private boat with a guide for each activity.
Can you stay overnight on the Similan Islands?
No. Overnight stays on the islands ended in 2018 and daily visitor numbers are now capped, so the Similans are visited as a day trip. In practice that means a base at Khao Lak on the mainland, which is closest to the crossing, or Phuket, which adds road time to the start of the day. We put people at Khao Lak the night before so the boat can leave early.
Journeys That Include This
Ask about The Similan Islands
We build it into a journey written from scratch around your dates, rather than fitting you to a fixed itinerary.
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