Safety

She Followed Every Rule and Still Got The Bends

A textbook Open Water course in Koh Tao. No fast ascents, no missed stops, medically cleared by a cardiologist who is also a diving specialist. Five hours later she couldn't walk.

By Mat Mora · Updated 31 July 2026 · ~14 min read

Who is Julia?

Before the story, it matters who this happened to, because it isn't who most people picture when they imagine a decompression accident.

From

Munich, Germany

Job

Pilates instructor

Trains

Hyrox, marathon, bootcamp, HIIT, cycling

Alcohol

None

Travelling

Long-term solo traveller, in Thailand when it happened

Diving experience

Student, mid Open Water course

She is, by any reasonable measure, one of the fittest and most careful people who will ever sit on a dive boat. Her body is also her livelihood. "A healthy body is my most important resource for my job," she told me. "At a certain point it wasn't sure at all if I would ever be able to just walk again."

The dives that went perfectly

Days one and two of the course never went deeper than 10 m. On day three the group did two dives: the deepest of the whole course at 18.9 m (logged as 18.0), then a second at around 15 m.

Here is her own summary of how those dives went:

• Inside the no-stop limits the whole time.
• Safety stop at 5 m, exactly as taught.
• No fast ascents. Others in her group got ascent-rate warnings from their computers. She never did.
• No panic, no buoyancy problems, no yo-yo profiles.
• Hydrated, well slept, sober, extremely fit.
• Fully disclosed her heart condition before she ever signed up.

Afterwards the group went back to the dive school, filled in logbooks, took photos, got smoothies. Completely ordinary. Around three hours after surfacing, Julia felt suddenly, heavily tired and went back to her hotel to lie down.

Three hours later

Lying on the bed, the room felt like it was still moving, as though she were on the boat. Then light flashes started at the edges of her vision, never in the centre.

She has had migraines her whole life. So she did what any of us would do: she filed it under "probably a migraine," and went to sleep. This is the trap. Type II DCS, migraine and stroke share a symptom set almost exactly.

Symptoms after a dive are not always dramatic and not always immediate. Fatigue, dizziness, visual disturbance, pins and needles, weakness or "just feeling off" in the hours after a dive should be treated as possible DCS until a diving physician says otherwise, even if the dive was textbook, and especially if you have a reason to explain them away.

She woke two hours later, roughly five hours after the dive. The boat feeling was worse. She was violently nauseous. She tried to get to the toilet and her legs simply would not carry her. She fell on the floor, threw up three times, and then crawled out of her room and knocked on a stranger's door.

"That's not decompression sickness"

The neighbour, a stranger she had never met, walked her to the nearest dive school, which wasn't the one she was training with, because dive schools have oxygen.

That dive school was not concerned at all. Their answer, in her words: *you don't get decompression sickness when everything went well. That's just not something that happens.*

They did call her own dive school, whose driver came and took her to the hospital. But sit with that first response for a second, because it's the reason this article exists.

"You only get DCS if you make a mistake" is not true, and it is dangerous. Julia was told this on the course. It is one of the most persistent myths in recreational diving, and it costs people time. Time is the only currency that matters in a DCS case.

Her view now is blunt: *"Dive schools like to pretend it's something that never really happens, and if it happens then you have one session and you're good again."*

A chamber with no doctor

Koh Tao is a small island with a state hospital and, separately, a hyperbaric chamber run by an association. The chamber is operated by a genuine diving expert. She is not a doctor.

The island has no cardiologist, no neurologist and no diving physician. With Julia presenting with a congenital heart condition and strong neurological symptoms, the call was made that treating her there was too dangerous: if anything went wrong inside the chamber, nobody on the island could manage it. Straightforward type I cases, they can handle. Hers wasn't one.

The hospital did the single most important thing right: 100% oxygen, started soon after she arrived, and kept on all night, through the transfer, only coming off for the toilet and for phone calls to her insurer. Every time it came off, she says, the symptoms came straight back.

Then the weather closed in. The speedboat to Koh Samui couldn't run that night. She waited out the storm on oxygen, with no definitive treatment, until the next morning.

She reached the chamber on Koh Samui and got her first hyperbaric session roughly 30 hours after the dive.

My honest opinion on those 30 hours

I want to be careful here, because I wasn't in the room and the people on Koh Tao were making a judgement call about a patient with a heart condition and no specialist backup. That is a real risk and I take it seriously.

But there is a question worth asking out loud, because it applies to every remote dive destination on earth: the chamber operator could have picked up a phone. A doctor on Koh Samui, a diving physician anywhere in the world, a 24/7 dive-medicine hotline. Remote telephone consultation with a hyperbaric specialist is normal practice, it is free, and it takes minutes.

With medical direction on the line, an early recompression on the island might have been possible. Untreated neurological DCS is not a neutral state. Bubbles keep doing damage while you wait. In my view the risk of doing nothing for 30 hours deserved at least as much scrutiny as the risk of treating her.

Before you dive anywhere remote, find out two things: where the nearest chamber is, and whether a doctor who can run a treatment is actually there. A chamber on the map is not the same as a chamber you can be treated in. Ask the dive centre directly and don't accept a vague answer.

€2,500 to start treatment

The private hospital on Koh Samui was, in her words, very professional at first: bloods, eyes checked because of the visual flashes, X-ray, a full workup.

Then everything stopped while they waited for her insurer to confirm payment. Her insurer didn't come back quickly. So Julia, unable to walk, called them herself and offered to pay out of her own pocket. The hospital agreed to start on a €2,500 deposit. She paid it without hesitating.

Her first session was nearly six hours in a single-person chamber, a glass tube you lie down in, like an MRI. No walking around, no toilet, adult nappies, Netflix on a screen outside with speakers inside, and a nurse who kept fetching her favourite snacks from 7-Eleven. The second session was another six hours, the third about two and a half, and the rest around 90 minutes each. Roughly ten sessions in total.

The diagnosis: decompression sickness, type II.

Better, discharged, then worse

After the first treatment she felt dramatically better for about 24 hours, so they discharged her. On her parents' advice she booked a hotel close to the hospital, which turned out to be one of the best decisions anyone made.

She was sitting by the pool chatting to another guest when it came back. It got worse and worse until, once again, she couldn't walk on her own.

On her second admission the symptoms were severe enough that the staff initially thought she was having a stroke: the entire left side of her body was numb and weak.

Relapse after apparent improvement is a known pattern in DCS. It is not a sign that the first treatment failed. It is a sign that treatment isn't finished.

The doctor who said three was the maximum

This is the part of Julia's story that made me want to publish it.

After three sessions, a doctor at the hospital told her, and told the nursing staff, that nobody ever needs more than three hyperbaric treatments. He refused to give her any more. She still could not walk unaided. She is a Pilates instructor. Her body is her income.

There is no such rule. Treatment continues until the diver stops improving between sessions, which for serious neurological cases regularly means five, ten, or more. She would eventually have around ten.

She was given Xanax and pregabalin, presented to her as treatment for the decompression sickness. Her read, looking back, is that it was there to calm her down.

What happened next is remarkable. Julia and her parents got on the phone and lined up:

• Diving physicians in Germany.
• A diving doctor in the Philippines, put in touch through her dive insurance, who gave her his personal WhatsApp and told her to message any time.
• Her insurer's medical team, who confirmed in writing they would pay.
• The German embassy in Bangkok, which called the hospital directly and told them to keep treating her.

Every external specialist said the same thing: she needs more treatment. The hospital refused anyway. Julia has her own theory about why one clinician wouldn't back down, and I'm not going to speculate on it here. The pattern is what matters to you: a single confident doctor overrode four independent specialists, an insurer and an embassy.

Her insurer's fallback plan was to move her to Bangkok. She couldn't fly at altitude, so that meant a low-altitude helicopter at around €80,000, more delay, and more risk, since a helicopter still can't fly at sea level.

How she got herself treated

So she called the hospital's insurance and management contact into her room and laid out the facts calmly. Roughly:

1. Name the avoidable harm: "We can do it your way, which is incredibly bad for me, because I lose time and I'm put at a risk that is completely avoidable if you just keep treating me."
2. Name the financial exposure: "My insurer is not going to be happy paying €80,000 for a helicopter that exists only because you refused. They will come after you for it."
3. Name the legal exposure: "And if I'm left with permanent damage, and it isn't clear that it wasn't your fault, I will file a lawsuit against you."

An hour later she was showering and being prepped for the chamber.

I don't think anyone should have to do that from a hospital bed while half their body is numb. But if you ever need to: be calm, be specific, put it in terms of consequences, and involve your insurer, your embassy and an outside diving physician early. It worked.

What "undeserved DCS" actually means

Undeserved DCS is the real term used in dive medicine for decompression sickness that occurs on a dive well inside accepted limits, with no procedural error. It is not rare enough to be a curiosity, and it is the reason the myth Julia was taught is so damaging.

Your dive computer is not measuring your body. It runs a theoretical model (usually Bühlmann ZH-L16C, or a variant) that treats you as a set of imaginary tissue compartments absorbing and releasing nitrogen at fixed rates. It's an excellent model. It's still a model, built on averages, and you are not an average.

Read the fuller explanation in our guide to what decompression sickness is, and how the planning behind those limits works.

The PFO question

The most likely explanation in Julia's case, still unconfirmed, is a PFO: a patent foramen ovale.

A PFO is a small flap-like opening between the two upper chambers of the heart. Everyone has one before birth. In roughly a quarter of adults it never fully seals. Most people live their entire lives without knowing, because it causes no problems on land.

Underwater it matters. After a normal dive your venous blood carries microbubbles that the lungs filter out harmlessly. With a PFO, a pressure change (a cough, a strain, lifting a tank, a Valsalva) can shunt blood right-to-left through that opening, and the bubbles bypass the lung filter and go straight into the arterial circulation, towards the brain and spinal cord. That is exactly the mechanism behind unexplained neurological DCS after modest, well-conducted dives.

The cruel part: a PFO does not show up on a standard echocardiogram or a cardiac MRI. Julia had both, and both were clear. Finding one requires a dedicated bubble study: agitated saline injected while you strain, watched on ultrasound. She describes it as an unpleasant test, which is a real part of the decision she now faces.

Present in

~25% of adults

Symptoms on land

Usually none

Shows on normal echo / MRI

No

Found by

Bubble study (contrast echo)

Why it matters diving

Bubbles bypass the lung filter

She followed every single rule, and that's the point

Line it up. Julia satisfied every layer of protection the recreational diving industry offers:

Every box ticked. Type II DCS anyway. Which tells you something uncomfortable and useful: the standards are a floor, not a guarantee. They are built for the statistical middle of the population. If you have any reason to think you're not in the statistical middle, the floor is not enough on its own.

If you have a pre-existing condition, be 10x more careful

This is personal for me. My own mum has a heart condition, and I have spent years telling her she should try diving. After talking to Julia I've completely changed how I'd approach that.

Notice that Julia's clearance was about as good as clearance gets. Not a form ticked at a resort desk: a cardiologist who had known her since infancy, who turned out to be a diving specialist too, with recent ECG and cardiac MRI in hand, who reasonably concluded that someone running marathons and doing Hyrox was not going to be troubled by a 18 m dive.

He wasn't negligent. He was looking at the wrong risk. Cardiac fitness answers "can your heart handle the exertion." It does not answer "could a bubble cross from the right side of your heart to the left." Those are completely different questions, and only the second one puts bubbles in your brain.

So if you, or someone you love, has a heart condition, a lung condition, a clotting disorder or anything else on the medical questionnaire, here is what I would now do:

1. See a diving physician, not just your specialist: Your cardiologist knows your heart. A hyperbaric or diving medicine physician knows what pressure does to it. Ask specifically about right-to-left shunt and PFO, by name. If your doctor doesn't dive, get a second opinion from one who does.
2. Ask directly about a bubble study: For a congenital heart condition, a history of migraine with aura, or any unexplained neurological symptoms, ask whether a contrast echo bubble study is warranted before you dive. Better an unpleasant test on land than a chamber in a place with no cardiologist.
3. Dive nitrox on air limits: Nitrox means less nitrogen in every breath. Plan the dive on air tables or air settings, then breathe EAN32: the extra oxygen buys you a wider inert-gas margin for free. It is not a guarantee against DCS, but it is one of the cheapest conservatism upgrades available, and it's a short course.
4. Use conservative gradient factors: Modern computers let you tune how close to the theoretical limit you're willing to sit. A conservative setting (for example GF around 40/70 rather than a stock 50/85) gives you deeper, earlier off-gassing and more margin. Rental computers on a course are usually locked to shop defaults, so ask what they're set to, and consider owning your own. See what a dive computer actually does.
5. Cap your depth and slow everything down: Most of the best light, colour and marine life is shallow. I've shot photos at 38 m and mostly thought about air and distance from the surface. Staying above 18 m, ascending slower than required, and adding time to your safety stop costs you nothing you'd miss.
6. Dive within reach of a working chamber: Not a chamber on a map. A chamber with a doctor. Ask before you book.

None of this is medical advice, and I'm not a doctor. It's what I'd want a friend to consider before getting in the water with a known condition, and it's what I'll be saying to my mum.

What it cost, and why insurance is not optional

The final bill was around €20,000, which she says is unremarkable for this kind of treatment. She paid none of it. That outcome was not luck, it was paperwork.

Read that first row again. Forty euros a month covered a twenty-thousand-euro emergency. She even bought it after leaving Germany, which cost her a slightly higher premium.

The other lesson is subtler and just as valuable: your insurer is not only a payer, it is a resource. Her dive insurance is what put a genuinely excellent diving doctor in the Philippines on her WhatsApp. When she needed leverage against a hospital, her insurer's confirmed commitment to pay is what she used.

• Check chamber and evacuation cover explicitly. Hyperbaric treatment and medical evacuation are the two expensive things. Confirm they're named in the policy.
• Save the 24/7 emergency number offline, in your phone and on paper, before you travel. In an emergency you may not be the one dialling.
• Know your policy number and cover limit. Julia lost hours to a payment confirmation that hadn't come through.
• Be ready to pay a deposit and reclaim it. Access to a chamber can hinge on it.
• Ask your dive centre what insurance is included with your course. Julia's was free and it mattered.

What to do if you think you have DCS

If you take one practical thing from Julia's story, take this. Print it, screenshot it, whatever.

1. Treat any post-dive symptom as DCS until proven otherwise: Unusual fatigue, dizziness, visual flashes, nausea, joint pain, pins and needles, weakness, confusion, trouble speaking, skin marbling. It can start minutes or many hours after surfacing. Don't wait to see if it passes. Don't sleep on it.
2. Get on 100% oxygen immediately: The single most useful thing you can do before a chamber. Every dive centre has oxygen. It reduces symptoms and it starts working on the bubbles. Julia's symptoms improved on oxygen and returned every time it came off. Stay on it.
3. Lie flat, keep drinking, don't get back in the water: Fluids help. Never attempt in-water recompression.
4. Call a dive-medicine hotline, not just the nearest dive shop: Your dive insurer's 24/7 line, or DAN's emergency hotline for your region (diversalertnetwork.org, daneurope.org, danap.org). A diving physician on the phone outranks anyone standing next to you who tells you it's nothing.
5. Do not let anyone talk you out of it: Two dive centres told Julia it couldn't be DCS. One doctor told her three treatments was the maximum. Both were wrong. If your gut says something is wrong with your body, escalate: insurer, embassy, an outside diving physician. You are allowed to insist.
6. Keep going until you stop improving: Treatment ends when repeated sessions stop producing improvement, not at some arbitrary session count.

The part nobody prepares you for: doing it alone

Julia was travelling solo. When her legs stopped working, the person who helped her was a stranger in the next hotel room whose name she didn't know.

Everything after that, the negotiating, the phone calls, the deposit, the hospital that wouldn't treat her, she handled from a hospital bed on an island on the other side of the world from everyone who loves her. Her dad flew out later. For the worst part, she was on her own.

I keep coming back to how avoidable that specific piece of it was. Koh Tao is full of divers. If any one of us had known, someone would have been at that hospital within the hour. Divers show up for each other: that solidarity is the best thing about this community, and it's completely useless if nobody knows you're in trouble.

It's a big part of why we built Diving Standard the way we did. Not just logs and planning tools, but a way for sea lovers to connect with the divers who are actually around them, join local groups, and not be a stranger in a town full of people who share your obsession. If you're travelling alone, find your people before you need them.

Would she dive again?

A month on, she is not back to normal. She can walk. Her Apple Watch still shows a walking asymmetry between her legs that was never there before, which for a Pilates instructor is not a small detail.

Two things are true at the same time here, and she is careful to keep them apart.

The diving itself, she loved. "It was so calming, being under the water. I swam with the fish and I was always like, hi fishy." Three days into a course, she had already found the thing that hooks all of us. Nothing about being underwater frightened her.

What traumatised her was the undeserved DCS and everything that followed it. Collapsing on a hotel floor. Being told twice it couldn't be what it obviously was. Thirty hours of waiting. A doctor who stopped treating her. Weeks of not knowing whether she would walk properly again. That is the part she describes as one of the most traumatic experiences of her life, and none of it happened in the water.

So when I asked whether she'd dive again, her first answer was the one you'd expect: *"I wouldn't have done it in the first place."* And then she said something I genuinely wasn't expecting:

*"Definitely not as long as I don't know where it came from. But if we find out it's a PFO, and I talk to a diving specialist, and the specialist tells me: if you do this and this differently you'll be more than fine, or just don't go that deep, then maybe I would try again."*

She isn't deciding yet, and she shouldn't have to. Her plan is to take her time, sit with it, recover properly, and see how she actually feels in a few months rather than a few weeks. *"I will just see wherever it takes me."*

But she is clear that if she does go back, it will not be casually. A real diving specialist first, paid for by the insurance she calls far too expensive. A definitive answer on the PFO. Shallower dives. Every precaution she can stack up, all of them in place before she gets in the water. That is exactly the right order, and after the month she's had it is more openness than most people would have left.

Julia agreed to tell this story because she thinks divers are not being told the truth about how bad DCS can get, or that it can happen when nothing goes wrong. She's right. If this article means one diver takes an odd symptom seriously three hours after a dive instead of going to sleep, it was worth her time.

Thank you, Julia. Get well properly, and keep us posted.