Khao Lak Diving Season: Best Months, Closures & What to Expect
When to dive from Khao Lak: month-by-month conditions, Similan season dates, low-season options, and how to choose between day trips and liveaboards.
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Last updated November 2026. The Khao Lak diving season runs roughly from November to April, with January to April the busiest stretch. The Similan and Surin parks close for part of the year, typically from mid-May to mid-October. Dates between those windows are the ones that need planning.
Featured image: Pedro Krtička, CC BY 3.0, via Wikimedia Commons.
Quick answer: the Khao Lak diving season at a glance
Peak season is roughly November to April, when Andaman Sea access to the Similan Islands, Koh Bon and Koh Tachai is most reliable. Late October and early May are shoulder months, and boats may or may not run. From about mid-May to mid-October the parks are closed and the sea is rougher. Our Khao Lak diving overview covers the wider picture.
Water stays warm all year. Expect roughly 26°C (79°F) at the cool end and 31°C (88°F) at the warm end. Visibility in peak season can pass 100 ft (30 m), though it varies by site, tide and weather. Our Khao Lak water temperature guide has the detail by month.
Month-by-month Khao Lak diving calendar
Read every cell as typical, not guaranteed. Sea state shifts year to year, and national park closures are set by the authorities. Check the Department of National Parks notice for exact current dates. For park access from town, see our Similan Islands day trip guide.
| Month | Park access (typical) | Sea state (typical) | Realistic plan | Best for |
|---|---|---|---|---|
| November | Reopening; boats ramp up | Settling | Similan day trips, early liveaboards | Fewer crowds |
| December | Open | Mostly calm | Day trips and liveaboards; book early | Holiday travelers |
| January | Open | Calm | Full site menu, busiest period | Fixed dates, big-animal hopes |
| February | Open | Calm | Similans, Koh Bon, Koh Tachai | Whale shark window begins |
| March | Open | Calm | Full site menu | Mixed-experience groups |
| April | Open | Mostly calm | Last full month of access | Late-season trips |
| May | Closing around mid-May | Turning rough | Local sites only after closure | Flexible divers |
| June to September | Closed | Rough, swell-prone | Boonsung Wreck and nearby sites if boats run | Patient, flexible divers |
| October | Closed until about mid-October | Improving | Local dives, then early reopening | Shoulder-season bargains |
Peak season: what to expect from November to April
January to April brings the longest runs of calm seas and the highest demand. Similan day trips and liveaboards fill early, so pre-book when your dates are fixed. Our Khao Lak dive sites guide lists the site menu.
Big-animal timing is a tendency, not a promise. Whale sharks are linked to roughly February to May, with Richelieu Rock the best-known site. Koh Bon is associated with manta rays, and Hin Daeng and Hin Muang suit confident divers because of currents. For resident wildlife year-round, read our Khao Lak turtle guide. Park depths run about 8 to 40 m.
Shoulder and low season from May to October
From about mid-May to mid-October the Similan Islands National Park closes. Many liveaboards pause, and day trips from Khao Lak become unpredictable. Visibility drops, cancellations rise and the site list shrinks to what boats can reach safely.
Local diving is still possible when the weather allows. Boonsung Wreck, Khao Lak: Depth, Level & Trip Guide is the main local option to ask about. Water stays inside the 26–31°C (79–88°F) range. Non-divers and mixed groups can look at Khao Lak Snorkeling: Best Trips, Season and How to Choose instead. Travelers fixed on May to September dates may prefer the Gulf of Thailand, around Koh Tao and Koh Samui. It is not a short hop from Khao Lak, so price the transfer first.
Day trip, liveaboard, or local dive: which fits your dates
Match the format to your dates and tolerance for boat time. Day trips need an early pier departure plus a hotel transfer, and the ride to the park is long. Liveaboards cut the daily commute and add dives. Local dives are the fallback when the parks are closed.
| Criteria | Similan day trip | Liveaboard | Local dive |
|---|---|---|---|
| Time at sea | Long boat ride each way | Sleep aboard, least transit | Shortest |
| Dives per day | Fewer | More | Fewer |
| Seasickness risk | Moderate to higher | Moderate | Lower |
| Cost tier | Middle | Higher | Lower |
| Certification | Often Open Water or above | Often Advanced for remote sites | Open Water or Discover Scuba |
| Flexibility | Weather can cancel | Fixed itinerary | Easiest to reschedule |
Costs, booking and logistics
Cost drivers are park fees, boat type, trip length and season. As of November 2026, no published rate is quoted here. For budgeting only, an illustrative example: a peak-season Similan day might be quoted near ฿4,500, while a local-site day in July might be near ฿3,000. Treat these as placeholders and replace them with real quotes. Compare shops through our Khao Lak dive shops list. Sea Dragon Dive Center is one example to read. You can also browse the SSI dive center locator.
Ask these before paying:
- Do you refund or reschedule if the weather cancels the trip?
- Is the national park fee included in the price?
- What is the maximum group size per guide?
- Is nitrox available, and at what extra cost?
- What minimum certification does the site require?
- What time is the pier departure, and how long is the hotel transfer?
Where to stay and how to get around
Pick a base close to your shop's pickup point. Early pier departures mean a hotel transfer before sunrise, so sleeping near the coast road saves time. Ask the shop for the pickup window when you book, and keep your first morning free in case boats reschedule.
Common mistakes when planning Khao Lak diving dates
Avoid these planning errors:
Peak-season visibility can pass 100 ft (30 m), while shoulder-month trips lose clarity and face more cancellations.
- Booking non-refundable Similan days in shoulder months such as late October or early May.
- Expecting guaranteed whale sharks or mantas; sightings are never promised.
- Assuming the Gulf of Thailand is a short hop from Khao Lak.
- Ignoring the park closure notice from the national park authority.
- Skipping the cancellation policy before paying a deposit.
Notes for your next dive trip
Optional updates to our Thai diving guides.
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