Phuket vs Koh Tao: Which Thai Dive Base in 2026?
by Yannick SchrothAug 26, 20266 min read
Photo: Eli Duke, Wikimedia Commons, CC BY-SA 2.0.
Best for
- Year-round diving, the cheapest certification and the most independently assessed operators: Koh Tao
- Similan liveaboards and an island with more going on than diving: Phuket, mid-October to mid-May
| Phuket | Koh Tao | |
|---|---|---|
| Signature | Similan day trips and liveaboards | The cheapest certification anywhere |
| Season | Similans shut mid-May; the reopening date differs by source | Year-round |
| Operators we list | 60 | 60 |
| In the Green Fins register | 8 | 28 |
| Assessed in person | 8 of 8 | 24 of 28 |
| Tier spread | 1 Gold, 4 Silver, 3 Bronze | 4 Gold, 18 Silver, 2 Bronze, 4 Digital |
| Certification cost | We did not verify one | PADI Open Water around $340 |
| Instructor languages | Not published by any of the 60 | Not published by any of the 60 |
| Visa | Thailand's DTV | Thailand's DTV |
| Best for | Liveaboards, in season, and a bigger island | Certifying, and diving any month |
Phuket in short
Phuket is the larger, better-connected base, and its reputation rests on trips that do not start there. The Similan Islands are a day trip or a liveaboard from Phuket rather than a Phuket dive site, and Mu Ko Similan National Park closes them annually for roughly five months. The Tourism Authority of Thailand's park listing gives 16 May to 14 October; reporting for 2026 gives slightly different days. Two official-side sources disagreeing is itself the finding: check the current year's announcement rather than trusting any single date, ours included. Book a Phuket dive week inside that window and you have booked somewhere else.
On the checking side Phuket is thinner than its size suggests. Of the 60 operators listed, 8 are in the Green Fins register, and all 8 hold an in-person assessment from the last twelve months: 1 Gold, 4 Silver, 3 Bronze. That is a real credential and it covers about one operator in eight.
Koh Tao in short
Koh Tao is small, dives all year, and is the cheapest place in the world to get certified: our Koh Tao guide puts a PADI Open Water course at around $340 and living costs at roughly $470 to $625 a month. It is a two-to-four-week island rather than a long base for most people, and it can feel small and party-heavy if you stay.
What it also has, and what surprised us when, is the checking. 28 of its 60 operators are Green Fins members, 24 of them assessed in person within the last twelve months, and the tier spread runs 4 Gold, 18 Silver, 2 Bronze and 4 Digital. On raw operator count the two islands are level. On independently assessed operators Koh Tao has three times as many.
Phuket or Koh Tao: the short version
If you are certifying, or if you are traveling between mid-May and mid-October, Koh Tao is the straightforward answer: it is cheaper, it dives every month, and more of its operators have had somebody visit them. Phuket earns its place when the Similans are open and you want a liveaboard, or when you want an island that is not only about diving. Both sit under the same Thai visa, so the decision is season and checking, not paperwork.
One thing neither island offers: not one of the 119 operators across both lists publishes which languages its instructors teach in. If that matters to you, it is a question for the shop and not for a register.
Phuket or Koh Tao: which to pick
- Certifying, or traveling May to October: Koh Tao.
- Similan liveaboards, mid-October to mid-May: Phuket.
- If independent assessment matters to you: Koh Tao, 24 assessed operators against 8.
- Either way, ask about instructor languages before booking. Neither island publishes them.
FAQ: Phuket vs Koh Tao
Is Phuket or Koh Tao better for diving?
It depends on the month and on what you want checked. Koh Tao dives year-round and carries far more independently assessed operators: 28 of its 60 are in the Green Fins register and 24 of those were assessed in person within the last twelve months. Phuket carries 60 operators of which 8 are in the register, all 8 assessed. Phuket's signature trips run to the Similan Islands, which the national park closes for roughly five months a year.
When are the Similan Islands closed?
Mid-May, on that all three sources agree. The reopening is where they part: the park's own page at the Department of National Parks gives 31 October, the Tourism Authority of Thailand gives 14 October, and the 2026 season was announced as 15 October. The disagreement covers the second half of October, so for those weeks confirm with the park before you pay for a liveaboard. The Similans are a day trip or liveaboard from Phuket rather than a Phuket dive site, so the closure decides what a Phuket dive week can contain.
Which is cheaper to get certified in?
Koh Tao, and by a wide margin: our Koh Tao guide puts a PADI Open Water course at around $340 and living costs at roughly $470 to $625 a month. Course and boat prices for Phuket are not published at a primary source, so no figure for them appears here. That is an absence in our research, not a claim that Phuket is expensive.
Does either publish which languages instructors teach in?
No. Not one of the 60 Phuket operators and not one of the 60 on Koh Tao publishes instructor languages anywhere we could read. If it matters to you, ask before you book; neither register carries it.
Sources
- Mu Ko Similan closing and opening dates, the park authority's own figure. Department of National Parks, Wildlife and Plant Conservation: closed 16 May to 31 October, open 1 November to 15 May, every year. nps.dnp.go.th. Read 7 September 2026.
- The 2026 season was announced shorter, 15 May to 15 October, for Mu Ko Similan and Mu Ko Surin together, under an order from the same department. The Nation. Read 7 September 2026.
- A third date, from the tourism authority, 16 May to 14 October, which is the one our other Thai pages carry. Tourism Authority of Thailand. tatnews.org. Three official-side sources, three reopening dates, all inside the second half of October.
- What an Open Water course costs on Koh Tao. The evidence is the shops' own price pages: Big Blue, Koh Tao Scuba Club and four more, set out with the reading dates on what an Open Water course costs on Koh Tao.
- What PADI charges for the eLearning half, which is billed separately from the in-water training: PADI store.
- Green Fins membership, assessment status and tiers for both islands: the member register of the Reef-World Foundation with the UN Environment Programme, greenfins.net. Read 26 August 2026. What separates an assessed member from a registered one is set out by Green Fins itself: certified membership against digital membership.
- Operator counts come from the SSI training-centre locator, divessi.com, read 26 August 2026. Both readings are recorded entry by entry on our Phuket and Koh Tao lists, which is where they are written down, not where they come from.