On January 7th, 2026, I went to my regular Wednesday night pool training—the first session of the new year—and experienced the scariest accident imaginable. I'm writing this post mainly to spread awareness about what happened. In all my years of freediving training, I've never heard of something similar happening to anyone. I hope people find this information useful and take their training safety seriously.

Background

I've been training regularly in the pool since 2016. Over the years, I've never stopped pool training for longer than a month, which was around Covid time. I've competed in countless pool competitions, attended world championships, experienced a few brief surface blackouts during static, and had one underwater blackout during dynamic over my years of training.

In the second half of last year, I had a period of a few months when I would do two long dynamic swims per week, and possibly one submax static as well. In total, last year I completed 30 DNF swims of 150m or more and 20 DYN(B) swims of 200m or more. Not to mention the countless short dives between 50m and 100m. My depth diving experience is more limited compared to pool, but I've reached 50m—limited only by equalization.

I had no medical conditions and wasn't taking any medications.

This is all to say: I'm not a beginner. I have plenty of experience training in the pool. Still, none of that could prepare me for what I experienced that day.

Incident

Pool training was around 7pm in the evening. I'd had a short break from dynamic training over the holidays, but I'd done a normal STA session four days prior. My last long dynamic dive was in late December, so I wasn't concerned about being out of shape. My goal for this session was to do a long DNF dive of around 150m in my new full-body 1mm suit and test the glide. The suit was the same standard size as my old sleeveless suit. It was somewhat tight, but that was expected for a new suit. Around the chest area, I felt it was still comfortable enough, so I didn't think the tightness would be an issue.

I used the same set of weights I always use. I packed my lungs with the same amount of air I always pack—still a lot, but not extremely so. I pushed off the wall and started the glide.

The first 15m, everything seemed fine. Nothing unusual. However, around then I started feeling something wasn't right. I can't remember now what exactly that feeling was, but if I had to guess, I think my arms and legs started feeling tingly. This is highly unusual at the beginning of a dive. That feeling progressed very quickly, and by 25m I knew something was going very wrong. So I surfaced and swam on my own to the side of the pool.

Then I realized I couldn't breathe.

Usually we take recovery breaths after a long dive, and this swim had barely lasted 30-40 seconds. There should be no reason to experience any fatigue or trouble whatsoever. Yet I just couldn't breathe. It's a really weird feeling when breathing simply stops and doesn't resume—there's nothing you can do to force it. That realization was terrifying.

My safety was there, not suspecting anything. After all, it's not unusual to stop a dive if you don't feel like it. Holding onto the wall, I somehow remembered reading somewhere that when people can't breathe on their own, it's still possible to use the packing maneuver (sipping air in with your mouth like through a straw) to "breathe" artificially. I tried to "breathe" like that while holding onto the side of the pool. I don't know if that helped me stay conscious, but I wasn't recovering or feeling better, in fact, it was getting worse. At one point I noticed my hand start to shake—similar to an LMC—and I felt that I couldn't control it anymore. Meanwhile, as this was happening, I felt squeezed and constricted by my new wetsuit. In my mind, the wetsuit being the only new variable, I had to get it off no matter what. In hindsight, that feeling was probably my limbs going numb and paralyzed. Somehow, I was still able to say a few words to my safety (surprising that my speech still worked). After a minute or so of me struggling, they probably realized something wasn't right. When they took off my weights and unzipped my suit, I still felt that wasn't enough, so I said "take it off" and "rip it off" a few times. I also remember saying "oxygen" once or twice.

By then, a couple of other people from the training group had come over to help. The pool lifeguards also noticed this (I was right in front of them, actually), and I suppose one of them went to get oxygen. Meanwhile, my safeties were trying to get me out of the suit and out of the pool. I remember having a strong cramp in my back that made it feel very stiff, and as they dragged me out of the pool, that felt quite painful due to the stiffness.

At that point, I was completely paralyzed and immobile. I was awake and could hear voices, but my vision was blurred. As I lay at the side of the pool and was given oxygen, only then did I slowly start to feel a bit better. I don't remember when normal breathing resumed, but I guess it was sometime then. However, I still couldn't move my arms or legs for a while. Slowly, I started to regain control—first of my fingers, then my hands and feet. They felt extremely heavy and sluggish at first. Perhaps after 10-15 minutes of lying down, I managed to slowly sit up. I was feeling weak, fatigued, and very wobbly. It took probably another 10 minutes to stand up with others' help, and I was still quite shaky and unstable walking.

I then sat for maybe 20-30 minutes, drank water, and slowly got better. I remember having to go fill out a form with the lifeguards. Writing was a bit hard, but I managed. I sat for a bit longer, and after about an hour or so, I felt almost normal. This was probably about 1.5-2 hours after the incident now. I managed to pack up all my gear and carry it myself to the place where we had dinner. We ate, and I was feeling quite normal—at least physically. I then took a cab home, showered, and went to sleep soon after.

Aftereffects

The following day, I started feeling various strange things across my body. At first, it started with very light tingling in my hands and feet/shins. The sensations were so subtle that at first I couldn't understand if I was imagining them or not. But with time they became more obvious, and after a day or so, they started to freak me out.

A couple of days after, the tingling subsided, but a feeling of weakness appeared in my hands. I still had strength—I could pick things up and make a fist if I wanted to. But when I let my hands rest, the sensation I had was weakness in both hands. That lasted on and off for a day or two.

On the morning of the third day, another persistent effect appeared that would show up every day since. A couple of hours after waking up, I suddenly started feeling a strong sense of something like dizziness and weakness. The first time this happened, I was walking outside, so I had to slow down. I remember thinking that if it got any worse, I might just collapse, but it seems my balance was never affected.

The best I can describe it is this: instability, giddiness, usually accompanied by some weakness in my legs (shins, calves, feet). It feels a bit like something wobbling/shaking/vibrating somewhere deep inside my head, usually accompanied by slight difficulty focusing—like a bit of a delay in being able to process information fast enough when walking. When sitting, I would still feel a light "buzz" (for lack of a better word) in my head, but it was easier to manage. By afternoon, these feelings would usually subside, and I would feel kind of normal. Sometimes they would return again in the evening.

Luckily, this got better after about three weeks. I could still feel some "buzz" in the mornings, but it wasn't as intense and overwhelming. That was probably the scariest aftereffect for me, as I didn't know what was happening or whether it would get better at all. At one point I got so concerned that I was afraid to go outside in the mornings because I didn't know what could happen.

Around the third week, I would often get a feeling of "pins and needles" in my legs while sitting—the kind of feeling when you sit in a bad position for a long time and your legs "fall asleep." Except I was getting that after only 5-10 minutes, and then some numbness would stay even when standing up or walking. And a similar thing in my arms sometimes when lying down. After the fifth week, this has mostly disappeared.

Apart from that, I definitely felt a lot of fatigue, especially in the first few weeks. It was hard to concentrate on work at the computer, and my eyes would get tired quickly. Sometimes I just had to go lie down for a bit. Usually, after a long sleep, I would be quite energized in the mornings. But after the incident, my energy is definitely not at the same level yet.

Investigations

I'll skip the long story of bouncing from one specialist to another over the course of a month. In short, I visited a GP, an ER doctor, a cardiologist, a pulmonologist, a diving medicine specialist, and two neurologists.

With all the above specialists, we did:

  • ECG (1st day after incident)
  • Another ECG and chest X-ray (2nd day)
  • Various neurological evaluations (2nd and 14th day)
  • CT scan of the lungs (2nd day)
  • Blood tests (2nd day)
  • Echo scan of the heart (1 week)
  • CT scan of the heart and PFO check (1 week)
  • Holter monitor for arrhythmia (1 week)
  • MRI of the head (1 week)
  • MRI of the spine (2 weeks)

The only thing that showed up was a small 7mm lesion/cavity surrounded by an infection in my left lung. The pulmonologist made it quite clear that such a lesion could not have occurred recently (e.g., on the day of the incident) but was likely developing for weeks or even months. I was prescribed antibiotics for a week. One month later, we did another CT scan of the lungs, and everything was clear. The doctor said it wasn't clear from the blood tests what exactly the infection was.

One day after the incident, some friends connected me with a couple of divers from Taiwan who seemed to have had something similar happen to them. They were kind enough to share their story and diagnosis of AGE—arterial gas embolism. In their case, however, the paralysis was in half of the body. They also had scans clearly showing the air bubble. After researching AGE, it seemed to me like the most likely explanation.

However, when I mentioned AGE to the doctors, most of them were skeptical about it. I'm not exactly sure why, as most of them didn't really explain, but I suspect it's because:

  • I was fully paralyzed, whereas with AGE it's usually half of the body (as with strokes).
  • The depth I was diving at in the pool wasn't nearly deep enough—most of them are probably only familiar with AGE in scuba divers.
  • The tests and evaluations showed nothing—in a classic textbook AGE, the symptoms would probably be more serious.

Honestly, the whole experience of talking to doctors was quite frustrating. I do trust that they're qualified and know what they're doing. Yet none of them could explain or even suggest a theory of what happened to me.

Theory

Since the doctors couldn't give me a plausible theory, I still lean towards AGE. Here's what I think happened:

The high pressure in the lungs (full breath + packing) and the lung infection present at the time, together created a small tear in the lung. This tear creates a direct connection between the air spaces and blood vessels in the lungs. Gas bubbles are pushed into the pulmonary veins, which carry blood from the lungs to the left side of the heart. From there, the heart pumps these bubbles out into the aorta, the body's main artery. The bubbles can then travel into any artery branching off the aorta. The vertebral arteries, which run up the neck to supply the back of the brain and brainstem. Once in the vertebral arteries, bubbles can block blood flow to critical areas controlling balance, vision, breathing, and consciousness, causing symptoms like severe dizziness, loss of coordination, visual problems, difficulty breathing, or even loss of consciousness.

In fact, this theory emerged after a discussion with Dr. Bizo Silva, a freediving researcher, who suggested the bubbles might travel via the vertebral arteries (which then join into the basilar artery). He also speculated that my face-down position during the DNF dive might have facilitated the bubbles taking that route. Because these arteries lead to the brainstem, blocking blood flow may result in full paralysis—unlike the half-paralysis that occurs if the bubble goes into the carotid arteries and then further, affecting one hemisphere of the brain.

AGE is similar to a stroke—in both cases, blood flow to the brain is blocked, depriving tissue of oxygen. In the case of a stroke, it's a blood clot blocking the artery. With AGE, it's air bubbles (emboli) doing the blocking. The mechanism is the same, and the aftereffects are the same as well. So now I sometimes just tell people "I had something like a stroke" to skip the detailed explanation.

As for the brain MRI showing nothing, that's still a bit of a mystery. Typically, you would see even "mild" strokes clearly on an MRI long after they happened. There's a thing called a transient ischemic attack (TIA), which lasts only a few minutes and the tissue manages to recover. But with TIA, there are usually no aftereffects. Otherwise, it's also possible that the damage is microscopic and falls below detectable limits.

How Do I Feel?

I'm better, thanks for asking. Most aftereffects have disappeared or become less intense after a month.

After more than five weeks, I still feel somewhat overwhelmed and uncomfortable in places with lots of noise, people, or traffic. Walking, talking, or looking at a screen can all feel tiring. Sitting or lying in an uncomfortable position for a while can make my body feel strange as well. And if I don't get enough sleep, I feel completely destroyed the next day.

Immediately after the incident and in the first week, I was feeling quite shaken psychologically, but also had a sort of peace—just happy to be alive and somewhat functional.

After that, with all the physical weirdness coming and going, it started to get tough mentally. Not knowing what was going on, not knowing if it would get better or worse, not getting much help from the doctors, having only a few people to talk to about this—all of that was taking its toll and left me somewhat depressed. One day I even experienced a panic attack, and the feeling of dread stayed around for a few days.

I also felt a bit down about not being able to do freediving. Something I'd spent so much time and energy on was taken away so suddenly. What was all that effort for?

I'm probably fit enough now to start some light training—it should be fine. But I can't imagine at the moment training again for competitions and doing long dives. I just don't know how to deal with the possibility that within a minute after packing your lungs with air and starting a dive, you could be struggling for your life. That feels like too much of a risk to take. Maybe I'll slowly get over it, maybe not. Not sure.

Outro

Thanks to my safeties XQ, ZB, and Matt, who rescued me. Thanks to the lifeguard who brought oxygen quickly. Thanks to Tom for the support and numerous health discussions.

Health is precious. No competitions, trainings, stunts, or games are really worth the risks if you can avoid them. Dive safe, and please have an oxygen tank nearby.