On Scuba Diving in Thailand: The Course That Changes Every Dive to Follow

I wiggle my feet in the sand, surprised by the absence of broken coral. Overhead, fish dart out of the enormous cave before me like bats, and bubbles fly from my regulator as I exhale, sinking slightly to stand flat on the ocean floor.

We can’t go in. No one in my group is certified for cave diving, and the boundary is non-negotiable. One of our guides, Jenni, hooks a thumb over her shoulder—it’s time to turn. We drift along the rock face instead, following the coral-covered wall as it disappears into the blue.

Forty kilometers off Krabi’s coast, the Phi Phi Islands are a gold mine for divers—dense with hard and soft corals, and the life that thrives around them. Topside, southern Thailand’s coastline is instantly recognizable—towering limestone islands scattered across the horizon, taller than they are wide. The view from the beach is enough to sell most travelers on the trip. But Krabi has another version of itself, and most of it is invisible until someone teaches you how to look. I came to learn.

Topside

Krabi is smaller than Bangkok and less famous than Chiang Mai, but that means it doesn’t feel like it’s trying too hard. Long, wooden motorboats are everywhere. One morning, I watched a pair of fishermen lean over the side of their’s and use what looked like a pitchfork to spear jellyfish, slopping them one by one into a big bucket in the middle of the narrow hull. “They use them for skincare and stuff,” Pauline, one of our instructors, said.

Almost everyone we met moved to Krabi impulsively, 10 or 20 years ago. The Europeans running Fast Manta, Zee,  the pastry chef at Phulay Bay who has her eye on a Michelin star, and the Georgian head of marketing at Banyan Tree. They each took the leap, and each stays for the same reason. When I asked Kari (the Finnish gentle giant who founded Fast Manta) why, he swung his arm wide, gesturing to the ocean and the mangroves, “Why would I want to leave?”

Krabi accumulates people who weren’t planning to stay. And Kari is one of them. A scuba diving holiday turned into opening a dive shop. And in March of 2026, the dive shop became the place where PADI launched a new chapter of its citizen-science work.

Our group was the first in the world to take PADI’s new Shark & Ray Conservation Specialty Course, and the first to log data into the Global Shark & Ray Census. The collected data is entered into a database that PADI analyzes, with the support of James Cook University, and feeds back to local governments to help inform their conservation policies. 

Last year, while reporting on the PADI AWARE Foundation, I learned that the global diving community has quietly become one of the largest citizen-science networks in the world—more than 6,600 PADI dive shops, and millions of certified divers, all trained to do something deceptively simple: pay attention. 

Beyond the data, these programs transform the way you dive. The reef you came to admire becomes a thing you are, in some small way, responsible for. The animals you see aren’t just pretty fishies; they are signs of health or distress. PADI AWARE’s citizen science programs give your dive a purpose beyond the stories you take home—beyond the photos and Go-Pro footage. They teach you to see.

Flipping Mushrooms

We are supposed to stay together. But, once you know that a mushroom coral on its back, overturned like a sad and helpless turtle, spends two weeks trying to flip itself back over—during which time it bleaches from lack of sunlight—it’s really hard to just keep swimming.

With their propensity to turn upside down, the fact that they have survived for over 240 million years is all the more impressive.

Breaking several rules at once, I leave my group and quickly fin over to a field of mushrooms on their backs—gently righting them. I cluster a few together, hoping proximity might protect them from currents. They are slick in my hands, exuding a thin film—a stress response. Several are dotted with splotchy white patches where their color has drained—or bleached. It will take time, but they can still heal—they haven’t gone fully white, yet.

It’s a small intervention. Temporary, maybe. But once you start to notice them, you see them everywhere.

“One of the easiest ways you can help a reef is to replant broken coral,” Andy tells our group, raising his voice over the boat’s motor as we speed toward our next dive site. He runs Coralyfe, a coral-restoration nonprofit based in Ao Nang. He is focused on teaching divers how to identify, log, and replant coral. Andy is an Italian marine biologist who, like nearly everyone here, came for a visit a decade ago and stayed.

When you replant broken coral, you don’t just set a fragment on a rock and hope for the best. You look for pieces that still have life (color) in them. Then you have to find a hole in a rock that holds it tight. After wedging a branch into a divot or sliding a piece of broken plate coral into a groove, you test the placement by wafting water at it, simulating a current. If it shifts, even slightly, it isn’t right. You have to start again. Sometimes it takes 10 minutes to find the right spot. Longer, if you’re particular. But the feeling of saving a small part of the ever-shrinking reef is extremely gratifying. 

Earlier that day, we’d been hovering, lowering ourselves close enough to see what was hiding in plain sight—a nudibranch no larger than a fingernail. Not far away, a tiny seahorse is anchored to a piece of coral the same shade of yellow as itself. (Seahorses stay within the same few square meters all their lives, so once you find one, you can go back and visit it again and again.) But back on land, the scale shifts.

Phulay Bay, a Ritz-Carlton Reserve , was designed in 2010 by the Thai architect Lek Bunnag, and everything in it is oversized. Beds the size of two kings joined the long way, lampshades five feet tall, bathtubs that could easily seat four. 

The detailing borrows widely: Lanna-inspired elements from northern Thailand, Moorish accents from much further west, deep purple and rust-orange interiors, hand-painted screens, keyhole doorways, and private tropical gardens with their own swimming pools.

Sharks and Propaganda

“There’s no photography allowed until you become an advanced diver,” Jenni explains to me. “So that’s another reason it will be good to get that certification.” I couldn’t agree more. Depending on memory alone to relive a diving experience is its own kind of gut-wrenching nostalgia. 

Later that day, my diving buddy, Kari, and I hover just above the sand, tucking ourselves into the shadows at the edge of the bay, trying to become as unremarkable as possible.

On the matter of Black Tip Reef sharks, they are numerous, indifferent, and better company than most.

Movement scares them off. Noise does, too. Even our breathing starts to feel too loud. We wait, and soon, Kari points excitedly as two blacktips emerge from the cloudy water to swim through the shallows in loose, squiggly lines. They’re smaller than I expected; not at all the looming presence I built them up to be. They are shy, tentative, darting away from things that feel unfamiliar to them.

Every shark we see, even if we can’t be sure if we saw the same one twice, is logged in the PADI AWARE app.

With us for the week was Brendon Sing—PADI’s regional manager, the founder of Shark Guardian UK, and the co-author of two children’s books that read, more or less, as anti-anti-shark propaganda. Most of Shark Guardian’s work happens in classrooms, on Zoom or in person, in schools all over the world: the patient business of explaining to kids what sharks actually do for an ecosystem, and what they don’t do to people.

The misconceptions matter because the math is really bad. Since 1970, oceanic shark and ray populations have declined by 71%. More than a third of all species are now threatened with extinction—up from a quarter. The driver, in nearly every case, is overfishing: fins, gill plates, liver oil, and bycatch from fisheries that weren’t targeting them in the first place. Sharks reproduce slowly, so they can’t bounce back the way other species can.

When sharks disappear, the rest of the reef goes with them. Without sharks, mid-level predators boom. Those predators eat herbivorous fish—the ones that graze algae off the coral. Without grazers, algae take over. The coral suffocates. The reef stops being a reef. This is the part Brendon spends his days explaining to children: that sharks aren’t villains, they’re critical infrastructure. And not all sharks look alike. 

One morning, we motored an hour offshore to a site I couldn’t see. Open water in every direction. Then Jenni pointed at a patch where the waves were slightly white-capping. Just a stutter on the surface. That, she said, was it. Kari explained later that kari, in Finnish, means “sunken rock” or “sunken island.” Exactly what we were looking at.

We’re here to visit Leopard sharks.

Indo-Pacific leopard sharks—also called zebra sharks, depending on which side of the world you grew up on—are listed as endangered on the IUCN Red List (that’s really bad). Both Kari and Pauline have leopard shark tattoos, marking encounters they don’t want to forget. Kari talks about them the way other people talk about the northern lights. We descended in a loose group. The bottom was sand and shadow, and the reef growing on and around the “kari” looks healthy here. After about 20 minutes, we saw it—a leopard shark sleeping on the sand in a small inlet. 

Our group hung suspended above it, doing our best to remain as silent as possible so as not to disturb its rest. But our breathing was loud, and eventually it swum off into the blue, clearly confused by this audience of bizarre-looking creatures. 

Sharks are famously feared for their teeth and huge, powerful jaws. Leopard sharks’ mouths are not even visible—positioned on the bottom of their head, close to the ground. All the better for catching small crabs and crunching through their shells. This particular kind of shark is downright cute. The babies are striped, which is why they’re also sometimes called zebra sharks. The spots come later. This one, roughly 5 or 6 feet long, powerful and fluid, swims with its whole body—unlike other sharks that use mostly their tails. It is the most beautiful animal I have ever seen. 

We surfaced and motored back to Fast Manta’s dock in a kind of daze. Typically, when back on the boat, snacks and sodas are passed, and the Fast Manta crew erupts into happy chatter and teasing. That day, we sat, staring at each other—broad smiles and sparkling eyes replaced the jokes for a while, before the crew’s infectious personalities bounced back into action. Pauline was literally bouncing. 

In the Trees

Banyan Tree, Krabi is built into the cliff above the bay, and the lobby is famous for its reflection pool—a thin sheet of water that all but erases the boundary between you and the horizon.

Dinner is in a tree, literally. One of the resort’s restaurants has tables and booths shaped like enormous nests, woven baskets perched in the branches big enough for four or five people to settle into. 

It was bug season, but it always is. Within minutes of sitting down, the staff began working around us. They brought small fans for our legs, then bug spray, then started turning off lights to give the insects less to chase. Above us in the dark canopy were the bats—the only sign of them being an occasional swoop overhead or the sound of a large fruit seed dropping into the leaves below.

The food was exceptional. We ate looking out over the bay, sipping cocktails that tasted exactly like mango sticky rice. It’s the same horizon of limestone islands we spent the day exploring, but now they are dimming into silhouettes as the sun drops like an egg yolk behind the glowing rim.

Filing back to our rooms after dinner, pleasantly full and exhausted, I realize how much greener Banyan Tree is than Phulay Bay. Huge banana leaves droop over the sidewalk, and the incline takes you straight down the mountain to the pristine, technically public beach, where you’ll find every kind of activity you could hope for. If Phulay Bay is a palace, Banyan Tree is the summer beach house. The rooms are beautiful and organic, sized for a human rather than a giant; the purples, reds, and rust oranges are traded for sage green, cream, and wicker.

The Elder

PADI’s most-joined program is much older than the Shark & Ray Census, and shaped by a different question: not what’s in the water, but what shouldn’t be. Dive Against Debris sends divers down to find and remove garbage.

Trash (like almost everything else in the ocean) moves with the currents. Some places end up with more than others. Like Malaysia, the world’s fifth-largest source of ocean plastic, which has stretches of reef where debris floating on the water’s surface is dense enough to block sunlight from the coral below—effectively suffocating it.

Other places get a slower, more international rotation. Brenden said you can usually tell how long a piece of trash has been in the water by how read able the packaging still is, and where it came from by what language it’s printed in. The mix that washes onto Krabi changes with the seasons. The week we were there, we mostly found fishing gear—long lines tangled deep into the coral. Extricating them feels like untangling a necklace. As frustrating as it is satisfying.

Taking in the scenic view from the cliffside is the easy part of visiting Krabi. The rest takes longer to see. On our last evening, we went to the night market in Ao Nang. It surprised me how safe it felt. People moved with strollers through the lanes—between stalls of clothing, bags, leather goods, and knick-knacks. Parents lifted children onto their shoulders to watch fire dancers working a crowd. Though there were many tourists and plenty of colorful gifts begging to be haggled over, it was a vacation that felt rejuvenating rather than overstimulating.

PADI AWARE’s programs aren’t an alternative to a vacation in southern Thailand. They sit inside one. The dive shops are the dive shops you would have booked anyway. The boats are the same. The resorts on the cliff above the bay haven’t asked you to give anything up. The work asks for the one thing you can’t outsource: your attention. And in a world where our attention is an asset, it’s a small gift you can give.