Where — and when — should you send diving and snorkelling clients in Thailand? The single most important fact first: the Andaman's flagship dive parks, the Similan and Surin Islands, close every year from mid-May to mid-October for monsoon safety and reef recovery — they reopen 15 October 2026, so right now is the moment to pre-book the November–April season. The rest of the map: Richelieu Rock for whale sharks (liveaboard only), Hin Daeng/Hin Muang off Koh Lanta for oceanic mantas, Koh Phi Phi for leopard sharks, and — counter-seasonal in the Gulf — Koh Tao, the busiest learn-to-dive island on earth, plus Sail Rock. This guide from a Thailand DMC for travel agents maps the dive regions and their seasons. Start with our Thailand destinations hub.
Explera is a TAT-licensed Thailand DMC trusted by 340+ agency partners, with in-house transport, boat charters, 24/7 support and IATA accreditation (96215733) — liveaboard berths, day boats and marine-park permits arranged as one confirmed program.
The Andaman — season-critical, world-class
Similan & Surin Islands
Granite boulder swim-throughs, sloping coral reefs, mantas and seasonal whale sharks make the Similans a top-ten global dive destination — reached almost entirely by liveaboard from Phuket or Khao Lak. The neighbouring Surin reefs are among Thailand's healthiest shallow systems, superb for snorkellers too. Both are inside national parks that physically close mid-May to mid-October; February–March is the visibility sweet spot. Book liveaboards early — the season is short.
Richelieu Rock
A horseshoe pinnacle east of the Surins and Thailand's number-one whale-shark site, also rich in mantas and world-class macro. Liveaboard access only, best February–April — the crown jewel of any Andaman dive file.
The southern Andaman
Hin Daeng and Hin Muang (the latter Thailand's highest submerged wall) off Koh Lanta rival Richelieu for oceanic mantas — advanced divers only. Koh Phi Phi's Bida walls and Shark Point deliver leopard sharks for beginner-to-intermediate divers, and Koh Haa's calm Lagoon is ideal for snorkellers and new divers. Pair the diving with the islands in our Koh Lipe and Trang islands guides.
The Gulf — Thailand's other, counter-seasonal coast
When the Andaman is closed, the Gulf is at its best (roughly March–September). Koh Tao certifies more divers than anywhere on earth — the natural learn-to-dive base — while Sail Rock, with its famous vertical chimney, and the Chumphon and Southwest Pinnacles bring barracuda schools and whale sharks. Koh Nang Yuan's Japanese Gardens is the postcard snorkel-and-viewpoint day. Because the coasts are counter-seasonal, Thailand always has a good dive coast open — a genuine year-round selling point.
Reef health — sell it responsibly
After the 2024 global bleaching event, Thai authorities temporarily closed several dive sites and marine parks to aid recovery — which has since outpaced early fears, with no active bleaching reported in the latest updates. The lesson for agents: book responsible operators (mooring buoys, no-touch, marine-park-fee compliance), keep itineraries flexible around any short-notice conservation closures, and position Thailand's season-closures as a conservation strength, not a limitation.
How to package it — your Thailand DMC for travel agents
Diving files run on seasonal windows, liveaboard allotments, certification levels and park permits — exactly the things a ground partner controls. Our boat charter team and tours and activities team book the liveaboards and day boats; the full Thailand DMC services for travel agents wrap hotels, transfers and 24/7 support, tuned to the markets you sell in. Pair the underwater days with the surface itinerary in our yacht and sailing charters guide.
Selling notes for the trade
- Sell the Andaman for November–April only — Similan/Surin are closed mid-May to mid-October; pre-book the 15 October reopening now.
- Switch coasts for year-round diving — Gulf March–September, Andaman November–April.
- Match site to certification: Koh Tao and Koh Haa for beginners; Richelieu, Hin Daeng and the pinnacles for Advanced Open Water.
- Whale-shark windows sell: Andaman/Richelieu February–April; Gulf late March–May and September–October.
- Book responsible operators and keep flexibility for conservation closures.
Frequently asked questions
When can you dive the Similan Islands?
Only from mid-October to mid-May — the Similan and Surin national parks close for the monsoon and reef recovery every year, reopening 15 October 2026, with February–March the best visibility.
Where are the best whale sharks in Thailand?
Richelieu Rock (Andaman, liveaboard-only, February–April) is the premier site; in the Gulf, Sail Rock and the Chumphon Pinnacle deliver whale sharks from late March–May and September–October.
Is Thailand good for learning to dive?
Yes — Koh Tao certifies more divers than anywhere on earth, with calm bays and dense PADI/SSI centres, making it the natural base for first-time divers.
Can you dive Thailand year-round?
Effectively yes, by switching coasts — the Andaman is best November–April and the Gulf March–September, so a good dive coast is always open.
Build dive files around the seasons that actually matter — with a Thailand DMC for travel agents that holds the liveaboard berths. Send us the dates and certification levels and we'll return a diving program ready to quote.
