Phuket Diving Season: When the Similan Islands Are Open
by Yannick Schroth
Aug 15, 2026
5 min read
Photo: No Troubles Just Bubbles, Wikimedia Commons, CC BY-SA 4.0.
Key takeaways
- All 8 register members were assessed in person within the last twelve months. The spread is 1 Gold, 4 Silver and 3 Bronze.
- Mu Ko Similan National Park closes annually for roughly five months, mid-May to mid-October. Two official-side sources give slightly different days, so check the current year's announcement rather than trusting any single date, including ours.
- The Similans are a day trip or liveaboard from Phuket, not a Phuket dive site. Distance and closure together decide what a Phuket dive week can contain.
- Not one of the 60 publishes which languages their instructors teach in. Ask before you book if it matters to you.
The closure is the first thing to check
The Tourism Authority of Thailand's own listing of park status gives Mu Ko Similan National Park as “Closed from 16 May until 14 October”, and adds that Ko Ta Chai, the island, beach and reef, is “Closed until further notice”. That listing carries a last-updated date of 7 July 2023.
Reporting on the 2026 season gives the closure as 15 May to 15 October, one day different at each end. We are not going to pretend to resolve that. Treat the closure as mid-May to mid-October and confirm the exact dates for your year with the Department of National Parks or with the operator taking you. The department's own portal carried no closure announcement on the day of reading, which is why the tourism authority is cited here rather than the park authority itself.
What is not in doubt is the shape of it: for roughly five months a year the best-known diving reached from Phuket is unavailable, and a page that sells you a Similan trip without saying so is not being straight with you.
Green Fins dive centers in Phuket
Green Fins is run by the Reef-World Foundation with the UN Environment Programme, and its assessments are made in person by trained assessors rather than by self-declaration. The register, read on 2026-08-14, carried 8 members in Phuket: 1 Gold, 4 Silver and 3 Bronze.
All 8 carry an assessment marked in person within the last 12 months. That completeness is worth more than the tier itself: it means the rating describes the business as it operates now rather than at some unstated point in the past. Every name and the evidence behind each field is on the Phuket operator list.
What the operators in Phuket Diving Season say about themselves
Separately from the register, each operator's own site carries more: 47 of the 60 responded. Training agencies they name themselves, which is their claim and not a check by anyone: SSI on 22, PADI on 17, TDI on 3, AIDA on 1, CMAS on 1 and RAID on 1. Fewer than half name any agency at all, which is lower than most places here, and it is a gap rather than a verdict. That comes from reading 47 sites, 148 pages in all. 6 more could not be read. The operator list for Phuket gives the page each name was read on.
Not one of the 60 publishes which languages their instructors teach in. A dive briefing is a safety briefing, so this is not a comfort question.
Weighing it against the other Thai base? Phuket vs Koh Tao puts the two side by side, including the register figures neither island advertises.
FAQ: Phuket
When are the Similan Islands closed?
Roughly mid-May to mid-October each year. The Tourism Authority of Thailand's park listing says 16 May to 14 October and was last updated 7 July 2023; reporting for 2026 gives 15 May to 15 October. Confirm the current year with the Department of National Parks.
How many Phuket operators are independently assessed?
All 8 in the Green Fins register carry an in-person assessment from the last twelve months. The spread is 1 Gold, 4 Silver and 3 Bronze.
Are the Similans in Phuket?
No. They are a separate national park reached from Phuket by day trip or liveaboard, which is why the closure changes what a Phuket dive week can contain.
Writes NOMADREEF and compiles its operator directory. This guide is desk research, not a trip report, and says so at the top. About the author
Sources
- Tourism Authority of Thailand, opening and closing status of Thailand's national parks, last updated 7 July 2023. Closure dates for Mu Ko Similan National Park, read 2026-08-14.
- Department of National Parks, Wildlife and Plant Conservation, portal.dnp.go.th. Checked 2026-08-14 for a current closure announcement; the portal carried none, which is why the tourism authority is cited above.
- Green Fins member register, Reef-World Foundation with the UN Environment Programme, greenfins.net. Membership levels and assessment status for 8 operators, read on 2026-08-14.
- Each operator's own website, opened between 2026-08-21 and 2026-08-26, for the training agencies they name. Recorded on our operator list.