Thailand (Similan & Surin Islands)

A morning at the Similans

The alarm on my phone vibrated at 4:47 AM, which felt absurd until I remembered why we'd set it. Maya, who'd chartered the 45-foot monohull through Phuket the week before, needed to catch the morning thermal for the run up to Ko Bon, and that meant clearing Yacht Haven Marina before the fishing traffic came loose. I stumbled into the cockpit with instant coffee that tasted like warm pennies, watched the sun refuse to come up for another hour, and listened to the VHF crackling with other boats doing the same calculation. By the time we'd motored past Phuket's deepwater anchorages and into open water, the granite spine of the northern islands was just a suggestion on the horizon — grey-green and improbable in the pre-dawn light.

This is what you come to the Similan and Surin Islands for, when you charter during the November-to-April window. Not the postcards. Not the idea of sailing in Thailand. The actual daily work of it: the planning, the compromise with wind and tide, the moment when you drop anchor in sand between two rock towers and realize the water's so clear you can see the bottom despite being fifteen metres down. When our BugBitten team planned this piece, we wanted to cut past the glossy sailing-magazine fantasy and give you the real shape of it — the hours, the irritations, the genuine magic that lives between them.

What makes this spot worth your time

The Similan Islands, lying roughly 55 nautical miles north of Phuket, offer something genuinely rare in modern Southeast Asia: a managed sailing ground where boats arrive faster than bureaucracy can corrupt it entirely. The nine islands (the name comes from the Malay word for "nine," though the administrative park technically covers more) are protected as Thailand's premier marine park, which means reefs aren't constantly shredded, fish populations remain substantial, and the granite formations that make the landscape so visually peculiar still stand without graffiti scarring the rock faces.

The diving here is legitimately world-class. Ko Similan itself — the largest in the group — has boulder-strewn walls that drop to 40 metres, with grouper, trevally, and the occasional blacktip reef shark patrolling the rubble. Ko Bon and Ko Tachai, the northernmost pair, sit above what Thais call "cleaning stations," spots where manta rays arrive with almost metronmic consistency to be groomed by smaller fish. I've seen exactly two mantas in my diving life; people who've chartered boats through this stretch routinely spot five or six per trip in the season. The Surin Islands, sitting another 60-odd nautical miles further north, carry an extra layer of remoteness — the water's emptier, the island village of Ao Bon still functions as a living settlement (not a museum), and the reefs feel slightly less hammered by daily traffic than the main Similan group.

Sailing-wise, the mechanics are equally appealing. The northeast monsoon, which dominates November through April, genuinely does push 10 to 18 knots across the Andaman with reasonable consistency. That's real wind, not the light chop that forces Australian sailors to motor two days out of three. The passages between island clusters run short enough to accomplish in daylight — usually four to eight hours, depending which way you're pointing. The sea state stays manageable outside the scattered squall season; you'll see lumpy days, but a proper storm surge is uncommon enough that locals actually note when one arrives. For sailors who've wrestled with Sydney's unpredictable wind patterns or learnt to accept motor-sailing as a fact of life, the Andaman in the season feels genuinely forgiving.

How the area feels

There's a peculiar compression to sailing northern Thailand. The granite islands rise without warning from surprisingly shallow water, creating a landscape that resembles nothing so much as an inverted map of Tasmania's mountains — the peaks underwater, the islands the stubborn bits that refused to sink. Your GPS tells you you're in open ocean, but you're almost always within arm's reach of something solid, which generates a strange intimacy with the geography.

The Similan group itself, by mid-morning, fills with other boats. Liveaboards arriving from Phuket, day-trip tour vessels disgorging snorkellers, the occasional superyacht. The mooring buoys (the park prohibits direct anchoring on reef) get claimed quickly, and if you're nursing coffee and watching the sun rise, you'll see the daily jockeying for position. It's not a crowded anchorage by Mediterranean standards, but it's busy enough that you lose the sensation of discovering something pristine. By contrast, the Surins, sitting 60 nautical miles further north, feel genuinely isolated. The ranger station at Ao Bon occupies a handful of buildings. A small Moken community — the sea-gypsies who once lived by free-diving and boat-dwelling — maintains a settled village ashore. Few day-trip operations run this far north, so your boat choices are limited to liveaboards willing to commit time.

The water itself feels alive in ways Australian anchorages often don't. The coral polyp activity is visible, especially at dusk. Fish behaviour is noticeably less skittish than in areas subjected to industrial fishing pressure. Beneath the surface, the Andaman feels like it still belongs somewhat to the creatures living in it, which is increasingly rare.

What to actually do here

Diving and snorkelling are the obvious water-based pursuits. The Tourism Authority of Thailand maintains a reasonable catalog of marine life present — groupers, snappers, trevally, the occasional tuna moving through deeper channels. If manta rays are genuinely your target (and they absolutely should be, given the statistical likelihood), Ko Bon and Ko Tachai are the main draw. Expect to see them in the November-February window. March and April are more hit-or-miss as water conditions shift. Most liveaboards operate with a dive master or guide included; if you're bareboat sailing, you'll need to either bring certified divers or accept snorkelling from the boat.

Beyond the underwater work, the islands themselves have limited infrastructure, which is partly the point. Ko Similan has a basic visitor centre and trails winding up the largest peaks — views are genuinely striking, though the trails are steep and often muddy. Ko Tachai hosts the wreckage of a historical fishing village; a few structures still stand, and the site offers a tangible sense of how people once lived on these islands. Ao Bon in the Surins is the main human settlement, where a respectful visit ashore reveals the Moken village and the ranger station. This requires sensitivity: you're not visiting a tourist attraction, you're crossing into someone's home. Bring gifts (fruit, toys for children, reef-safe sunscreen) rather than money, and approach as a neighbour would.

The sailing itself becomes its own occupation. Short hops between islands mean constant small-course decisions. Tidal planning matters — the spring tidal range runs nearly two metres, which creates genuine current in the channels. Night sailing, despite what Mediterranean glossies might suggest, stays risky because of the scatter of unlit fishing aggregating devices (FADs) anchored throughout the zone; most charter boats plan early-morning departures and aim to land before dusk, which comes fast near the equator. The practical reality of moving water and rocks under your boat, day after day, becomes meditative if you let it.

Provisioning is excellent in Phuket but absolutely non-existent once you head north. Before leaving the mainland, fill your water tanks, load the fridge, and stock the dry locker thoroughly. You won't find a shop at Ko Bon or anywhere else remotely north. Most crews plan a Phuket departure, possibly a night in Thailand (Phang Nga Bay) on the return journey, and return within 10 to 14 days.

When to go — and when not to

The season runs November through April. The first part of that statement is absolute; the second part matters more.

November and December deliver the steadiest wind, warmest relationships with the weather gods, and lowest odds of rain spoiling a dive day. Water temperature sits around 26–27 degrees Celsius, which is warm enough for thin wetsuits or rash guards. The season is also expensive and moderately crowded, particularly over Christmas and New Year, when charter prices spike and Phuket's bases run near full capacity.

January through early February remains excellent. Wind is still reliable, crowds thin slightly after New Year, and many consider this the sweet spot. Water temperature drops a degree or so, but remains perfectly swimmable. Air temperature stays warm but moves from "blazing" to "merely hot."

March and April are the end of the season, and the season is ending for a reason. Wind becomes less predictable and occasionally shifts toward lighter reaches. Squall activity increases. The water can turn cloudy as thermal conditions shift. Manta ray sightings become statistically unlikely by late March. Water temperature sits around 25 degrees. The upside: charter costs drop, crowds thin substantially, and the boats that remain tend to be skippered by professionals rather than holiday sailors. If you can accept less-than-ideal weather and don't need guaranteed manta encounters, March-April offers excellent value and reasonable sailing.

May onward brings the southwest monsoon and operational closure. The park authority implements seasonal restrictions, many charter bases reduce their fleet or close entirely, and weather becomes genuinely risky. Don't plan a trip during that window.

How to get there — and nearby worth considering

Nearly all charter operations base from Phuket, specifically Yacht Haven Marina (on the eastern side, toward Ao Chalong) and Ao Chalong itself. Flying into Phuket is straightforward for Australians — direct flights exist from Sydney and Melbourne, usually with Thai Airways or budget carriers. From the airport, ground transport to the marina takes 45 minutes by taxi or arranged car. Give yourself a day before departure to sort provisions, brief the crew, and shake down the boat.

If you're considering bareboat charter, expect to produce a valid skipper ticket (Australian recreational sailing qualifications work fine) and usually a security deposit. Skippered charters dominate the market because Thai national park authority requirements are stricter with independent crews — permits, registration checks, briefings on mooring protocols. The paperwork-to-sailing ratio tips strongly in favour of hiring a skipper, even if it costs more.

The itinerary flexibility depends partly on your boat and partly on the national park authority's mood on any given week. The standard run is Phuket to Ko Bon (two days), Ko Bon to the Surins (one long day or two short ones), and reverse. Alternative routes exist down the Similan chain, but northbound travel consumes most fuel and most time. If you're looking for nearby sailing grounds with different character, the Langkawi region sits about 200 nautical miles southwest and is accessible under engine or sail; alternatively, southern Thailand routes toward Surat Thani extend the season into other months. Many crews combine a Phuket charter with stops in Malaysia (Langkawi), though that requires careful fuel and provisioning planning.

The not-so-good bits

Let's be direct: sailing here involves bureaucratic friction that would exhaust a government employee.

Thai national park fees apply per person per day, and they've been revised upward recently. Budget roughly 400–500 baht per person per day. That's not extortionate, but across a crew of four over a 12-day trip, it adds up. Most importantly, you must carry cash. The park doesn't accept digital payment at moorings; you hand over notes when you register. Bareboat crews are often surprised by this, particularly Australian sailors used to contactless transactions.

The park authority controls your mooring options tightly. You can't simply drop anchor on sand where you'd prefer; you're directed to specific buoys, which fill by mid-morning during season. If you arrive at Ko Bon at 11 AM expecting a spot, you'll be moored a kilometre further out, which defeats the purpose of sailing close to interesting geology. Early arrival (before dawn if necessary) is non-negotiable if you want prime position.

Night sailing, as mentioned, carries genuine risk. The unlit fishing FADs scattered throughout the zone aren't theoretical hazards. Boats do hit them. Damage ranges from bent stanchions to mast-threatening impacts depending on approach angle and relative speed. Most charter crews adopt a conservative posture and time departures for daylight arrival. This sounds obvious until you're committed to a passage and the wind direction shifts at sunset, stranding you with a choice between approaching an anchorage in darkness or motoring inefficiently to eat time. It's not a tragedy, but it's a constraint.

Provisioning non-negotiables mean you're committed to a fairly rigid departure window. If you decide mid-trip to extend your voyage north, you can't simply do it; you're anchored without access to food or water. This forces an honest conversation with your crew before you leave Phuket about tolerance for being genuinely isolated.

The reefs, despite the protections, show wear. The Similan group particularly bears the marks of decades of heavy diving traffic and fishing pressure. The Surins are notably less impacted, but even there, the coral composition reflects past damage. If you've dived the Maldives or the Red Sea, you'll notice the difference. It's not dead reef, but it's recovering reef rather than pristine reef.

Finally, the weather genuinely closes the region seasonally. April arrivals risk being caught by deteriorating conditions. May through October is simply not viable for most charter operations. If you're flexible, this creates opportunity; if you've locked in January dates and can't move them, you're committed to accepting crowds and prices.

Practical essentials: gear, timing, realistic planning

Before you leave Australia, confirm your international Crew Certificate is in order. A notarized copy of your driving licence, your passport, and evidence of insurance are standard requirements for bareboat charters. Most brokers arrange Thai-language boat documentation, but you'll simplify things by arriving with clear records.

Water resistance matters. A decent windproof jacket, reef-safe sunscreen in volume, and polarized sunglasses for spotting underwater hazards are non-negotiable. The sun here is genuinely severe — worse than Australian autumn sun on the same latitude, because the water's brightness compounds the radiation. Invest in proper UV protection rather than discovering in day three that you've cooked your shoulders.

Bring your own medical kit with antibiotics. The nearest meaningful medical facility is Phuket; anything beyond first aid becomes a helicopter evacuation. Minor coral cuts can turn septic rapidly, so treat them seriously. Seasickness medication, if you're prone, matters — the passages between islands are generally gentle, but squalls can arrive suddenly and the chaotic fetch off the northern Andaman can surprise crews.

For Tours in Thailand, skippered options are abundant through the major brokers. Day-trip tourists rarely make it north of the Similans; the Surin cruises appeal to people with actual time and genuine curiosity about sailing rather than sight-seeing boxes to tick.

Plan a minimum of 10 days, realistically 12–14 days, to accomplish the run north to the Surins and back without feeling rushed. Shorter trips work if you're content staying in the Similan group, but the real remoteness and the statistically reliable manta encounters lie north. Calculate fuel costs — most modern charter monohulls will consume roughly 15–20 litres per day motoring, less under sail, but the variables are substantial enough that you want reserve capacity.

The UNESCO World Heritage List includes Phuket's nearby Phang Nga Bay, which offers an architectural perspective on how Thailand formally recognizes its natural inheritance. That said, the Similan and Surin groups currently sit outside UNESCO designation, which is arguably why they've remained relatively intact compared to some neighbouring zones.

Final word from the BugBitten team

Sailing the Similan and Surin Islands during the November-to-April window sits somewhere between a genuinely achievable adventure and a moderately complex logistical undertaking. It's not the hardest sailing in the world — the seasons are forgiving, the distances short, the anchorages protected. It's also not a brochure cruise; you're contending with real constraints (bureaucracy, tidal range, night-sailing risks) that force honest decisions about how much friction you're willing to absorb in exchange for the payoff.

What makes it worth the friction is the combination of real sailing — actual wind, actual distance, actual navigation rather than parking-lot cruising — paired with underwater ecology that still functions mostly as it should. The manta rays aren't a guarantee, but the probability is genuinely higher than anywhere else accessible to Australian sailors. The granite islands are genuinely unusual geology. The isolation of the Surins, once you commit to getting there, remains difficult to overstate in a world where everywhere feels vaguely connected.

If you're an experienced sailor comfortable with minor bureaucracy and willing to plan food purchases before departing, a skippered charter here will repay the effort. If you're seeking a soft tropical holiday with minimal decision-making, you're more likely to find it in Phuket's resort belt. But for crews ready to sail daily, wake early, navigate channels between rocks, and accept that the best anchorages demand discipline about timing — this corner of Thailand delivers the goods.