Destinations · Researched guide

Koh Lanta Diving: Hin Daeng, Hin Muang, and the Three Months They Are Closed

by Yannick Schroth Aug 15, 2026 5 min read

A Moorish idol over red reef at Hin Daeng, a dive site off Koh Lanta, Thailand

Photo: portioid, Wikimedia Commons, CC BY-SA 4.0.

Koh Lanta carries 6 operators in the Green Fins register and all of them have been assessed in person within the last twelve months, which is as complete as this gets. The catch is specific and easy to miss: Mu Ko Lanta National Park stays open, but Hin Daeng and Hin Muang, the two dive sites people come for, are closed from 1 July to 30 September. The park being open and your dive site being open are not the same statement.
Reefs, rules and operators all change. Confirm the current picture before you book.

How this guide was made, and what it is not. Nobody from NOMADREEF has dived Koh Lanta. This is not a trip report and it contains no first-hand observation, because inventing one would be worth less to you than saying so. It is built from sources you can open yourself, listed at the foot, and from our own reading of the Green Fins member register on 2026-08-14, which is the part you will not find elsewhere. Where a fact could not be confirmed at its primary source, it is marked as unconfirmed rather than repeated.

Key takeaways

Hin Daeng and Hin Muang close 1 July to 30 September, together with Ko Rok and Mu Ko Ha. The park itself stays open, so a page saying “the park is open” tells you nothing useful.
All 6 register members were assessed in person within the last twelve months. The spread is 5 Silver and 1 Bronze.
The closure covers exactly the months when cheap low-season accommodation appears. That is not a coincidence and it is worth planning around.
Not one of the 6 publishes which languages their instructors teach in.

The park is open. The dive sites are not.

The Tourism Authority of Thailand's listing of national park status gives Mu Ko Lanta National Park as “Open”, and then, in the same entry, lists what is not: “Ko Rok, Mu Ko Ha (Tukon Lima), Kong Hin Daeng - Hin Muang and Tham Khao Mai Kaeo (Khao Mai Kaeo Cave), and Ko Rok Campground - Closed from 1 July until 30 September”.

Read those two lines together, because separately each misleads. Hin Daeng and Hin Muang are the reason most divers choose Koh Lanta, and they are shut for a quarter of the year. A site that repeats only the first line is technically accurate and practically useless.

That listing carries a last-updated date of 7 July 2023, and the Department of National Parks portal carried no current closure announcement when we checked on 2026-08-14. Treat 1 July to 30 September as the shape of it and confirm your year with the park or your operator.

What the register shows

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. On 2026-08-14 the register carried 6 members in Koh Lanta: 5 Silver and 1 Bronze.

All 6 carry an assessment marked in person within the last 12 months, which makes this one of the more complete lists we have compiled. There is no Gold member here and no Restricted one either; it is a tight band. Every name and what each field rests on is on the Koh Lanta operator list.

What the operators say about themselves

Separately from the register we opened each operator's own site; 6 of the 6 responded. Training agencies they name themselves, which is their claim and not a check by anyone: PADI on 4, SSI on 2 and CMAS on 1.

Not one of the 6 publishes which languages their instructors teach in. Hin Daeng and Hin Muang are deep, current-swept sites where the briefing matters, so if you need it in a particular language, ask before you pay.

What we did not verify

Park fees, boat prices, transfer times from Krabi or Phuket, and monsoon risk windows are hard facts under our rules and were not confirmed at a primary source for this location, so they are not in this guide.

Questions

Are Hin Daeng and Hin Muang open all year?

No. The Tourism Authority of Thailand's park listing has them closed from 1 July until 30 September, along with Ko Rok and Mu Ko Ha, even though Mu Ko Lanta National Park itself is listed as open.

How many Koh Lanta operators are independently assessed?

All 6 in the Green Fins register carry an in-person assessment from the last twelve months. The spread is 5 Silver and 1 Bronze.

Is Koh Lanta worth it in low season?

That depends what you came for. The cheap months overlap the closure of the two best-known dive sites, so the saving and the loss are the same three months.

Yannick Schroth

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

What this guide is, and is not. This is independent research by the operator of this site, not reviewed by a lawyer and not medical or safety advice. Listing an operator is not a safety endorsement: we have not dived with these businesses, inspected their equipment or watched a briefing. Diving carries risk that no register removes. Every fact here carries the date we checked it, and anything we could not confirm is marked as unconfirmed rather than smoothed over. Confirm what matters before you book.

Sources

Tourism Authority of Thailand, opening and closing status of Thailand's national parks, last updated 7 July 2023. Status of Mu Ko Lanta National Park and the sites closed within it, 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.
Green Fins member register, Reef-World Foundation with the UN Environment Programme, greenfins.net. Membership levels and assessment status for 6 operators, read 2026-08-14.
Each operator's own website, opened 2026-08-14, for the training agencies they name. Recorded on our operator list.

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