SSS Chamber Network Phuket

A slightly long but innstresring and factual post from the husband of one of our patients

When Following the Rules Still Wasn’t
Enough
How my wife developed decompression illness on a liveaboard trip
in the Similan Islands, what we’ve learned and how we do things
differently
By Andrew Doyle
This is a personal account of one decompression illness incident, not medical or dive-
planning advice. Divers should follow their training, local procedures, their computers,
and advice from qualified dive-medicine professionals.
In November 2025, my wife and I were on a liveaboard dive trip in the Similan Islands,
Thailand. It was the kind of trip many divers look forward to: warm water, multiple dives
a day, beautiful sites, and the familiar rhythm of diving, eating, resting, and sharing
stories and pictures with fellow divers. By the end of it, though, we were dealing with a
serious decompression illness incident that reminded me how quickly a routine dive trip
can change.
My wife was not new to diving. She had more than 300 dives and many liveaboard trips
behind her, including the Great Barrier Reef, Raja Ampat, the Maldives and the Red Sea.
She is Advanced, Deep Diving and Advanced Wreck certified. I am a 58-year-old dive
instructor with a deep diving instructor rating to 40 metres, among other qualifications.
This was not a case of inexperience, unfamiliarity with repetitive diving, or a lack of
respect for the discipline required on a liveaboard.
We were not casual about our diving. We planned conservatively, used appropriate gas,
followed our computers, and stayed within the no-decompression limits set by both our
computers and the dive boat. We are both fit and otherwise healthy. And yet my wife still
developed decompression illness.
The Dive Trip
We were on a five-day trip with a professional operator. Our guide was a 27-year-old
Taiwanese instructor who was guiding only my wife and me. She stayed within the
prescribed limits, but she was more aggressive than I would normally be in trying to
maximise both time and depth and importantly, the rate of ascent.
The Dive
We were diving on Nitrox EAN32, using Mares Sirius dive computers. The liveaboard set
a maximum trip depth of 30 metres, even though we were certified to dive to 40 metres.
On the last dive, after which my wife showed symptoms, our maximum depth was 25.4
metres. We completed an extended stop of about eight minutes between 10 metres and
8 metres, followed by the obligatory three-minute safety stop at 5 metres. Her gradient
factor was 13 at the start of the safety stop and 5 at the end. At the surface, her gradient
factor was 57.
From a dive profile perspective, this was unremarkable. There was no obvious rule-
breaking. We were not drinking alcohol. We do not smoke. We were diving within our
planned limits and following our computers. On paper, this was not the sort of dive
profile most divers would point to and say, “That is where the problem started.”
The Symptoms & The Treatment
Her symptoms came on suddenly around 3 pm, within 15 minutes of completing the
dive. They were extremely serious: numbness down the right side of her body, partial
paralysis, dizziness, and a rash across her torso, classic DCS symptoms. We
immediately put her on 100% oxygen and treated the situation as a medical emergency.
I showed no symptoms despite us diving an almost identical profile.
She was transferred by ambulance boat to Khao Lak, then by ambulance to Bangkok
Siriroj Hospital, arriving about eight hours after the symptoms were first noticed and
oxygen was started. By then, with only 100% oxygen and IV saline, the rash had
substantially retreated. Around midnight, she was treated in a hyperbaric chamber on a
U.S. Navy Table 6 (USN TT6), followed after an eight-hour break by a U.S. Navy Table
5 (USN TT5). The care was covered by DAN dive insurance as well as our travel
insurance. Had we broken the rules, I doubt we would have been covered.
The e ect of the treatment was remarkable. She received no other medication, yet the
neurological symptoms began to resolve rapidly. Over the next three or four days,
however, her whole body became inflamed and swollen, almost like a Botero statue.
She put on about three kilograms of fluid and had aches and pains throughout her body
before the swelling and pain gradually subsided. Within five days, she was all but back
to normal.
Models Are Useful, But They Are Not Reality
My previous line of work was in options trading. In that world, we relied heavily on
models while also accepting that every model is only an approximation. A model helps
you make decisions, but no serious trader confuses the model with reality. The market
always has more variables than any model can capture. Black-Scholes, for example, is
powerful and useful, but it rests on assumptions that do not fully match the real world,
including the assumption that market returns are normally distributed. As a trader, I
would often say, “The model is wrong.” And when someone asked, “So what do you
use?”, my answer was, “The Black-Scholes model, because I don’t know anything
better.”
I have always understood decompression models in a similar way.
I have been diving since 1990, long before dive computers were available to most
recreational divers. I learned using dive tables. Those tables were a simple model, built
around a square profile: the assumption that you stayed at your maximum depth for the
entire dive. That made them conservative, but also limiting.
Dive computers changed everything. They account for changing depth throughout a dive
and continuously estimate on-gassing and o -gassing over time. They are extraordinary
tools, and they make recreational diving vastly safer than it would be without them. But
they are still modelling a personal biological process. They simplify something complex
and depend on assumptions that may or may not fit a particular diver on a particular
day. My Mares Sirius uses the Bühlmann ZH-L16C algorithm, which assumes that
di erent tissue compartments absorb under pressure and then release inert gas in
defined ways. I understand the model reasonably well, and I also understand that it has
limitations.
According to the model, she should not have developed DCS. But she did. One thing is
clear: the model was wrong in this case. To be clear, I am not saying the model is
fundamentally flawed. I am saying it is imperfect. It cannot capture every nuance, every
individual factor, or every circumstance that may contribute to decompression stress
and illness. It is a simplification.
Even so, when it happened to my wife, my instinct was to search for one clear cause.
What had we missed? Was there a mistake in the profile? Was there some obvious
factor we had overlooked? The more we looked, the more the answer seemed to be that
there may not have been a single cause at all.
The Chamber Conversation
When we attended the decompression chamber, I was still looking for the cause. Kevin,
the chamber manager, said something that has stayed with me: “95% of people who
come in here are following the rules.”
That sentence reframed the whole experience. It did not make the rules unimportant.
The rules matter. Training matters. Conservative planning matters. Computers matter.
Gas choice matters. Stops matter. But none of them turn diving into a zero-risk activity.
Contributing Factors
So what else was going on? In hindsight, one factor was that my wife was a little
dehydrated. She had also slept poorly the night before because of dampness in our
room. Neither issue felt dramatic at the time, and neither would necessarily have
mattered on its own. On a liveaboard, small discomforts can easily seem normal: warm
weather, repeated dives, disrupted sleep, physical e ort and the constant need to stay
hydrated between dives.
But decompression stress is not experienced by a theoretical diver. It is experienced by
a real person, on a real day, with that person’s hydration, sleep, workload, physiology
and accumulated exposure all forming part of the picture. Divers Alert Network notes
that decompression illness can occur even when accepted guidelines are followed, and
that known and unknown individual risk factors can influence the probability of an
incident.
The Dive Before
I now believe the incident may have started on the dive before the final one. As we were
preparing for the last dive, my wife mentioned some lower back pain. At the time, we put
it down to hauling heavy gear on and o the boat, but in hindsight I think it may have
been an early symptom. On the second-last dive, our maximum depth was 25 metres,
and we spent a long time at depth: we only came above 15 metres after 47 minutes of a
54-minute dive. We then ascended to 5 metres in about two minutes, at which point her
gradient factor was around 25. That was within limits and acceptable by the computer,
but it was faster than I would normally choose, especially after a long, deep dive. With
the benefit of hindsight, I should have slowed down the ascent, which is easy to say
after the fact. We completed the three-minute safety stop at 5 metres, with her gradient
factor around 9 at the end. Looking back, that profile now stands out to me as the more
likely point where the problem began.
What I Took Away
The biggest lesson for me is that decompression illness is not always a story about
recklessness. Sometimes it is a story about probability, imperfect models, and human
variability. A diver can do the right things and still have a bad outcome. That is an
uncomfortable truth, but it is important.
For divers, especially on repetitive liveaboard schedules, the lesson is not simply “stay
within your computer.” It is also to treat hydration, rest, warmth, workload, and honest
self-assessment as part of decompression safety. If something feels o , it is worth
taking seriously. If symptoms appear after diving, do not try to explain them away. Get
oxygen, contact appropriate medical support, and seek evaluation from people who
understand dive medicine.
I already understood that slow ascent mattered. I had always been uncomfortable when
a guide reached the three-minute mark at 5 metres and then went straight to the
surface. That final 5 metres matters. On my own dives, I often came up very slowly,
sometimes pausing at 1 or 2 metres while other divers were already boarding the boat. I
thought of it as a “super safety stop.”
At the time of the incident, we had already signed up for a decompression diving
certification, with an instructor rating for me. We completed it in December 2025. It was
a fantastic course with an excellent instructor, and it reinforced what I already believed:
understanding decompression better helps divers make more conservative choices.
Now, even on no-decompression dives, I pay closer attention to staged ascent
practices, extra time in the 6 metre to 3 metre zone, and my estimated surface gradient
factor. For any Advanced-certified diver who plans to dive beyond 18 metres, I strongly
recommend considering decompression diving training.
Did it stop my wife from diving? Not at all. A little over a month later, and only after being
cleared by an appropriate doctor, she was back in the water at one of her favourite
places: Tulamben, Bali, photographing nudibranchs, ghost pipefish, and other small
critters. Were we apprehensive? Yes, especially on the first couple of dives. We kept
things deliberately conservative, stayed shallower than 18 metres, and took about 15
minutes to resurface very slowly. But her confidence was not broken. She understands
the risk, and we both understand the contributing factors more clearly now. We have
adapted the way we dive, especially the way we ascend.
I am writing this not to suggest that dive computers failed us, or that training does not
matter, but to share a reminder that decompression illness can happen inside the
apparent margins. Those margins reduce risk; they do not eliminate it. My wife followed
the rules and still got bent. That is exactly why divers need humility, preparation, training
and a willingness to respond quickly when something is not right.

A little trip to Singapore for the AHDMA significant meeting updating our Knowledge

This course is valuable for all trip leaders, giving you a better understanding of first aid. Next course is planed for 5-9 Oct. Get in touch for more information

A big thank you to Chantelle for coming over and sharing her knowledge on the DAN DMT course. Also Deano Jenkins, Marja van Gerven, Kevin Black, Natthika Lek, Oliver, leathwood, Kevin Morgan for being great students, bringing a wealth of experience to draw on, and making the course interesting and fun.

If you are interested in this course, feel free to get in touch for further information.

We get asked the same question very frequently. It is a big misconception. We can help limit the risk factors but can not take them away 100 %

We wil be running a DAN DMT course 10-14 Aug contact us if you are interested and want more information.

With more mild HBOT treatments becoming more popular please be aware aware that cheap is not always the safest

The Critical Importance of Hyperbaric Oxygen Therapy Safety ⚠️ Hyperbaric News Two fatal hyperbaric chamber fires in 2025 highlight severe safety risks, underscoring the critical need for strict compliance with hyperbaric safety protocols.