The sun glints off turquoise waters as I hover weightlessly above a maze of corals. Twenty meters below, a green sea turtle glides effortlessly across the seafloor, its movements unhurried and deliberate. I adjust my buoyancy, watching bubbles spiral upward as the current gently pushes me over a garden of swaying anemones. This is the Similan Islands – where the water is so crystal clear that visibility stretches beyond imagination, where every dive feels like floating through an aquarium designed by nature herself.
I first heard about the Similans from Dave, a weathered dive instructor I met in a Phuket beach bar. “If you think this is good,” he’d said, gesturing toward the decent-but-touristy Patong shoreline, “wait till you get to the Similans. That’s the real Thailand underwater.” His eyes lit up as he described boulder formations and manta rays, and I knew right then – between sips of my Chang beer – that I had to see it for myself. Two days later, I was on a speedboat heading northwest from Khao Lak, salt spray in my face and anticipation bubbling in my chest.
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What I found exceeded every expectation. The Similan Islands stand as Thailand’s undisputed crown jewel for scuba diving – a marine sanctuary where pristine waters, extraordinary biodiversity, and a refreshingly laid-back atmosphere combine to create an underwater paradise that’s tough to match anywhere in Southeast Asia. In the pages that follow, I’ll take you on a deep dive (forgive the pun) into what makes this archipelago special, how to get there, and share hard-earned tips from my own adventures exploring these waters.
I don’t claim to know everything about diving – far from it – but after logging hundreds of dives across Southeast Asia over the past seven years and returning to the Similans three separate seasons, I’ve gained some perspective worth sharing. My obsession with underwater worlds has taken me from the Philippines to Indonesia, Malaysia to Myanmar, but something about these islands keeps pulling me back. Let me show you why.
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Why the Similan Islands Stand Out
The Similans comprise nine granite islands (though officially eleven since 1998 when neighboring Koh Bon and Koh Tachai were incorporated into the national park) scattered like emeralds across the Andaman Sea. Each island – numbered rather than named by most dive operators – rises dramatically from the ocean, fringed by beaches of powder-white sand that would make Caribbean postcards jealous.
What immediately sets the Similans apart is the water clarity. On good days, visibility stretches to 30 meters or beyond – I’ve checked my depth gauge at 25 meters and still clearly seen our boat bobbing on the surface. The water temperature hovers blissfully between 27-30°C year-round, making 3mm wetsuits perfectly comfortable (though I’ve seen plenty of hardy souls diving in just rashguards).
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But it’s what lives in these waters that truly captivates. On a single day of diving, I’ve watched blacktip reef sharks patrolling sandy channels, followed a hawksbill turtle munching on soft corals, and hovered mesmerized as a tornado of chevron barracuda spiraled above me, their silver sides catching sunlight like thousands of mirrors. The coral coverage remains impressive despite global bleaching events – massive colonies of staghorn and table corals spread across vast stretches, while brain corals the size of small cars create labyrinthine landscapes. Giant sea fans wave lazily in deeper sections, creating perfect frames for underwater photographers.
During my second trip, at the tail end of February, I experienced that magical moment every diver dreams about – a whale shark appeared suddenly from the blue at Koh Bon. The massive juvenile, maybe six meters long, cruised unhurriedly past our group, its distinctive spotted pattern hypnotic in the clear water. Our divemaster later told me we’d hit the jackpot – whale shark sightings, while possible, aren’t guaranteed even in peak season.
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Compare this to Thailand’s other diving hotspots, and the Similans’ appeal becomes even clearer. Koh Tao on the Gulf side offers convenience and affordability, perfect for certification courses, but its reefs have suffered from overcrowding and the visibility rarely matches the Andaman. The Phi Phi Islands have their charms but struggle with overwhelming tourism pressure – I once counted eight different dive boats moored at the same site there. The Similans, protected by national park status and geographical isolation, have largely escaped this fate. Despite growing popularity, they retain a frontier feel, an exclusive atmosphere that becomes apparent the moment you drop below the surface.
I’ll never forget my first dive at East of Eden, a site on the eastern edge of Island #7. As we descended along a sloping reef, a massive shadow passed overhead – my first-ever manta ray sighting. The creature, wingspan easily four meters across, performed a balletic turn above us, so close I instinctively ducked despite knowing we were in no danger. I nearly bit through my regulator mouthpiece from excitement, struggling to keep my breathing steady as I fumbled with my camera. The photos turned out terrible – a blurry dark shape against blue – but the memory remains crystal clear.
Top Dive Sites You Can’t Miss
What makes the Similans truly special is their diversity of dive environments. Whether you’re newly certified or sporting a technical diving patch, these waters offer something remarkable.
Elephant Head Rock
Imagine a submerged mountain that shattered into house-sized boulders, creating a maze of swim-throughs, caverns, and channels. That’s Elephant Head Rock (between Islands #7 and #8), arguably the most distinctive topography in the Similans. Dropping into this site feels like entering an underwater sculpture garden – granite formations worn smooth by currents, covered strategically with soft corals and anemones.
The site demands respect – currents can pick up unexpectedly, and I’ve had dives where finning against the flow felt like swimming on a treadmill. But that current brings nutrients, which brings fish – enormous schools of snappers, groupers lurking in crevices, and if you’re patient, the occasional reef shark patrolling the perimeter.
During my last visit, our divemaster Lek guided us through a narrow passage nicknamed “the chimney” – a vertical swim-through that opened into a cathedral-like space where sunlight filtered through in ethereal rays. We emerged to find ourselves surrounded by hunting trevallies, their silver bodies flashing as they corralled smaller fish against the rocks. Pure underwater theater.
Christmas Point
At the northwestern tip of Island #9 lies Christmas Point, named for its tree-like soft coral formations. The site features a series of submerged pinnacles starting at 12 meters and dropping well below recreational limits. The terrain creates natural channels that funnel nutrients, resulting in explosive marine life.
What makes Christmas Point memorable is the color. Unlike sites dominated by hard corals, here purple, red, and pink soft corals cover every surface, waving gently in the shifting currents. It’s especially magical in the morning light when sunbeams cut through the water column. During my December dive here, we spotted two leopard sharks resting on a sandy patch at 24 meters – their spotted patterns perfectly camouflaged until we nearly swam directly over them.
The site can be challenging when currents pick up, but there’s a protected area behind the largest pinnacle where less experienced divers can shelter while still enjoying the show. My tip: bring a reef hook (or dive with an operator that provides them) for those moments when you want to stay put and watch the action without fighting the current.
Koh Bon
Technically not one of the original nine Similans but included in the marine park, Koh Bon is manta ray territory. A horseshoe-shaped ridge extends from this limestone island, featuring a dramatic wall drop-off on one side and a shallow reef plateau on the other.
The wall dive is spectacular in its own right – look closely to spot ornate ghost pipefish, harlequin shrimp, and if you’re exceptionally lucky, the occasional guitar shark. But everyone comes for the mantas, which visit cleaning stations here with remarkable regularity between February and April.
On my first Koh Bon dive, we saw nothing larger than a grouper and surfaced slightly disappointed. Our dive guide suggested we try again in the afternoon when tidal movements change. Smart advice – thirty minutes into our second dive, three mantas appeared, circling the cleaning station where small wrasse picked parasites from their white undersides. We knelt on the sandy bottom (at a respectful distance), regulated our breathing to conserve air, and simply watched the show. When one manta barrel-rolled directly overhead, passing within two meters of my outstretched hand, I felt a connection I can’t adequately describe – eye contact with an intelligent creature clearly aware of our presence but unthreatened by it.
Richelieu Rock
Ask any experienced Andaman diver to name Thailand’s single best dive site, and chances are they’ll say Richelieu Rock. Technically part of the Surin Islands rather than the Similans proper, it’s included in most Similan liveaboard itineraries – and with good reason.
This horseshoe-shaped submerged pinnacle rises from 35 meters to just below the surface (though the very top is exposed at extreme low tide). What makes Richelieu extraordinary is its biodiversity compressed into a relatively small area. Every inch of the rock is covered with life – soft corals, anemones, gorgonian fans – creating a technicolor backdrop for marine encounters.
Current at Richelieu can range from non-existent to challenging, but it’s this water movement that makes the site so productive. On my last dive here, we hooked in at 22 meters and watched as the current brought the show to us – schools of barracuda, batfish, and jacks swirled in the blue, while titan triggerfish and Napoleon wrasse patrolled closer to the reef.
Richelieu is famous for macro life too – my dive buddy spent our entire safety stop photographing a tiny tiger-striped seahorse while I watched a pair of dancing harlequin shrimp nearby. February through April offers the best chance of whale shark encounters, though as with all wildlife, there are no guarantees.
My most memorable Richelieu experience came during a late afternoon dive when the current picked up unexpectedly. Rather than fight it, our guide signaled for us to go with the flow. We drifted along the outer edge of the pinnacle, carried at a brisk but manageable pace, watching the reef life unfold like a movie. Schools of fish parted as we passed, and a curious tuna investigated our bubbles. When we finally surfaced, half a kilometer from our starting point, I couldn’t stop grinning. Sometimes, diving isn’t about control but surrender.
Planning Your Similan Diving Adventure
Getting There
The gateway to the Similans is typically Khao Lak, a laid-back beach town about 80km north of Phuket. You have two main options for diving the islands:
Day Trips: Speedboats depart Khao Lak around 8am, reaching the nearest Similan sites in about 1.5 hours. You’ll typically get two dives, lunch on one of the islands, and return by late afternoon. Expect to pay 4,500-5,500 baht ($130-160) including equipment rental, lunch, and national park fees.
Liveaboards: Multi-day boats range from budget to luxury, typically offering 3-5 night itineraries with 3-4 dives daily. Prices start around 15,000 baht ($450) for a basic 2-night trip and climb to 60,000+ baht ($1,800+) for premium boats with private cabins and gourmet meals.
Having done both, I strongly recommend the liveaboard experience if your budget and schedule allow. Day trips feel rushed – just when you’re getting comfortable with the conditions, it’s time to head back. Plus, liveaboards access the more distant sites like Richelieu Rock, which are too far for day trips.
My first Similan experience was on a mid-range 4-day liveaboard. Accommodations were basic (shared cabin, communal bathrooms), but the diving schedule was perfect – early morning dives before other boats arrived, sunset dives when the hunting predators became active, and even a night dive at a sheltered bay. Falling asleep to gentle rocking and waking up already at the next dive site creates an immersive experience day trips simply can’t match.
Critical timing note: The Similans are only open from mid-October through mid-May. Outside these months, monsoon conditions create dangerous seas, and the park closes completely. Even within the season, conditions vary – early season (October-November) sometimes has reduced visibility from plankton blooms, while late season (April-May) brings warmer water and occasionally stronger currents. February-March typically offers the sweet spot of good conditions and marine life activity.
Choosing a Dive Operator
With dozens of companies offering Similan trips, choosing wisely matters. My criteria has always been:
- Group size – Smaller is better. I avoid operators who pack 6-8 divers per guide.
- Experience level – Do they regularly visit the Similans, or is it an occasional trip?
- Safety standards – Equipment condition, emergency oxygen, communication devices.
- Environmental responsibility – Do they brief on reef protection? Ban gloves to prevent coral touching?
Among the operators I’ve personally dived with, Wicked Diving impressed me with their conservation focus and small groups (maximum 4:1 diver-to-guide ratio). Sea Bees Diving runs a professional operation with slightly larger groups but excellent equipment. On the liveaboard side, The Junk and Pawara offer good mid-range experiences. For luxury, the Phinisi or Thailand Aggressor will spoil you between dives.
I’ve had particularly good experiences with smaller operations where the owners still lead dives themselves – their passion for the area usually translates to better briefings and site selection. If possible, visit dive shops in Khao Lak before booking – you’ll get a feel for their professionalism and potentially negotiate better rates in person.
Gear and Preparation
Rental equipment is widely available, but I’ve always preferred bringing my own mask, fins, and computer at minimum. If renting, check equipment thoroughly before departure – I once discovered my BCD’s inflator button stuck halfway to the dive site, requiring a last-minute swap.
Pack essentials most operations don’t provide:
- Reef-safe sunscreen (oxybenzone-free)
- Rashguard or thin wetsuit (3mm is plenty)
- Anti-fog for masks
- Dramamine if you’re prone to seasickness
On my first liveaboard, I woefully underpacked dry clothes, forgetting how chilly evenings can get after multiple dives. Now I always bring a light fleece for evenings on deck.
For underwater photographers, wide-angle setups excel at most Similan sites, though macro opportunities abound at Richelieu Rock and Koh Bon. Bring multiple batteries – charging opportunities on smaller boats can be limited.
Cost Considerations
Beyond the base trip cost, budget for:
- National park fees (currently 500 baht/day for foreigners)
- Equipment rental if needed (700-1,000 baht/day)
- Tips for crew and guides (10-15% is standard)
- Pre/post-trip accommodation in Khao Lak
One money-saving tip: many dive shops offer discounts for bringing your own gear or booking multiple day trips, often 10-15% off the standard rate.
Another consideration: book well ahead. During peak season (December-January), quality liveaboards fill months in advance. I learned this the hard way my second season when I spontaneously extended my Thailand stay but found every recommended boat fully booked.
Beyond the Dive—Exploring the Islands
The Similans aren’t just about what’s beneath the waves. Island #4 (Koh Miang) and Island #8 (Koh Similan) have ranger stations and basic facilities for day visitors. When my ears needed a break between dives, I discovered the islands offer their own simple pleasures.
On Island #8, a moderately challenging 20-minute hike leads to “Sailing Rock” (sometimes called Sailor’s Rock or Sail Rock) – a massive boulder improbably balanced on the hillside. The viewpoint offers a panorama that justifies the sweaty climb: azure waters stretching to the horizon, dotted with green islands and the white wakes of passing boats. I’ve spent hours here just watching the shifting patterns of light on water, occasionally spotting a sea eagle soaring overhead.
Island #4 features a less strenuous walking path leading to a small hidden cove perfect for snorkeling when conditions are calm. The beach itself is postcard-perfect – the kind of white sand that squeaks underfoot, lapped by crystal waters. After intense diving days, I’ve napped under palm trees here, lulled by the rhythm of gentle waves.
Wildlife abounds on land as well – fruit bats hang from trees near the ranger stations, monitor lizards patrol the undergrowth, and if you’re still enough, dusky leaf monkeys might peek at you from the canopy. Unlike Thailand’s more developed islands, there are refreshingly few food vendors or massage huts – just basic ranger facilities and the occasional information board.
This simplicity forms part of the Similans’ charm. Where Phi Phi and Phuket buzz with nightlife and commerce, the Similans offer only nature and silence. My most treasured memory comes from a late afternoon on Island #8 after our dive boat had departed and before the rangers urged remaining visitors to leave. For thirty minutes, I had an entire beach to myself – just me, the setting sun painting the sky in watercolor hues, and the gentle lapping of waves. After weeks in Thailand’s busier destinations, that solitude felt almost sacred.
The Last Ascent
As my dive computer ticks through the final minute of a safety stop on my last Similans dive, I find myself already missing these waters. There’s something about this place that gets under your skin – perhaps it’s the promise that every dive might bring an encounter with something extraordinary, or maybe it’s simply the pristine quality of a marine environment still largely intact despite the planet’s mounting pressures.
The Similans represent Thailand’s underwater crown jewels – unspoiled beauty, world-class diving, and an atmosphere increasingly rare in our over-touristed world. Despite growing popularity, they retain their magic through careful management and simple geography. When that whale shark glided past me, or when I locked eyes with a curious octopus tucked into a crevice, I felt the privilege of visiting their world rather than them performing for mine.
If you’ve read this far, I suspect you’re already reaching for your dive log and calendar. My parting advice is simple: go. Life offers too few perfect moments, and the Similans deliver them with remarkable consistency. Plan carefully, dive responsibly, and prepare to fall in love with a world beneath the waves that will call you back again and again.
My most perfect Similan memory isn’t of mantas or whale sharks, but of a simple sunset descent at Beacon Reef. As the day’s last light filtered through the water, painting everything in gold, I neutralized my buoyancy and simply hovered, suspended between worlds. The only sound was my breathing and the distant clicks of hunting fish. For those few minutes, all worries of work emails and travel logistics evaporated. I was exactly where I needed to be, doing exactly what I loved, in one of the most beautiful places on earth.
When you find yourself there – and I hope you will – I’d love to hear your own Similan stories. Every diver experiences these waters differently, finding their own moments of underwater magic. Your adventure awaits, just below the surface.