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Size, err Depth, Matters: Why Do Pools Keep Breaking Records?

The opening of the world’s first uber 33-meter deep swimming pool, NEMO 33 in 2004, kicked off an inevitable depth race that continues to this day. Now, with three increasingly deep, sub-30-meter pools in Europe, construction scheduled to begin on a new 50m deep pool in England, and a record-breaking announcement expected from Dubai, it’s fair to say that deep pools are here to stay. We asked dive travel blogger Florine Quirion to give us an in depth tour of the facilities and their uses, and explain why size, err depth, matters.



by Florine Quirion

Photo credits: pictures courtesy of Nemo 33, Y-40, DeepSpot and Blue Abyss. Freediving pictures at Y-40 by Stephen Mesureur.

When landlocked divers can’t travel, turning to diving pools to extend the fun and relaxing sensation of scuba diving can be the exact pressure release valve they need. Some scuba divers question the point of diving in a pool at all. But, since the early 2000s, Nemo 33 has been shaking up preconceived ideas of pool diving’s possibilities and utility, and so have its successors.

For ten years, the Belgian deep pool Nemo 33 held the record for the deepest pool in the world, until Y-40 opened in Italy in 2014. Since then, new deep diving pool projects keep popping up, each one promising to be the deepest in the world. With a new deep diving pool about to open in Dubai, is there any point in competing for depth besides free publicity?

Let’s do a roundup of the deep diving pools worldwide (all pools deeper than 30 m/100 ft are currently located in Europe). What has been the motivation behind these daring projects? Are there any takeaways for the diving community? Thanks to their 365-days-per-year stable conditions, it would seem so—in most cases.

Nemo 33: Maximum Depth 33 m/108 ft

Pioneers often start as dreamers. John Beernaerts, both a civil engineer and a scuba diving instructor, dreamt of recreating French Polynesia’s diving conditions right in the heart of Belgium. Beyond the catchy pitch, the idea was to provide divers-in-training with easier and safer conditions  than the murky and cold waters of the Belgian quarries.

Being the first to dare building such a deep pool wasn’t without challenges. Beernaerts produced the first sketches in 1996, and after three years of engineering studies (21 versions of the facility were simulated) and four years of construction, the pool opened in 2004.

Despite being the first to push the limit of what a deep diving pool can be, it is striking to note that Beernaerts wanted to make his project as sustainable as possible. By heating the pool water to 33°C/91°F  using solar panels, Nemo 33 uses less energy than a traditional swimming pool, which is usually heated 5°C/9°F lower.

Located in Uccle, in the southern suburbs of Brussels, it quickly became a scuba diver’s favorite place for a diving trip during the cold winter months. The pool has an internal volume of 2,500 m3/660,430 gallons and a surface of 20 m/66 ft by 16 m/52 ft. It features five depth platforms at -1.3 m/-4 ft, -2.5 m/-8 ft, -5 m/-16 ft, -10 m/-33 ft, and finally at the bottom of its shaft, -33 m/-108 ft. Scuba divers can also reach two air bells located at -9 m/-30 ft deep.

On many occasions, Nemo 33 has been used as an underwater studio for filming crews, a training facility by security professionals, and a research facility for scientific and medical hyperbaric studies. The diving facility keeps innovating by offering underwater exhibitions and even the possibility to book a table for dinner in the air bubble at 7 m deep in the pool. Thanks to its large reception areas and a renowned Thai restaurant, Nemo 33 has become a popular venue for incentive events and group trips.

When asked about the current race to the deepest pool, Beernaerts answered, “For us, after holding the record for ten years, it’s about being the safest diving pool in the world now. I can’t deny how much coverage holding the world record got us. We initially had an actual depth of 35 m/114.8 ft. After we lost the record, we decided to go backward and mount a platform at the bottom of the shaft to be precisely at 33 m/108 ft deep, as our name suggests. 

I remain perplexed about the new projects announcing 50-60 m/164-197 ft deep pools and their goals beyond the publicity. I’m more concerned about the level of awareness about nitrogen narcosis. With clear and warm water, the perceived easiness could tempt beginner divers to descend to depths they shouldn’t go. It’s vital to remain within the limits of one’s training.”

Nemo 33 remains the most affordable deep diving pool in the world. A dive for certified divers costs 25€/$30 USD, any day of the week. The fins, mask, BCD, and regulator were initially included in the fare, and you had only to bring your dive computer (or rent it at 3€/$3.62USD per day). However, to comply with COVID-19 safety rules, Nemo 33 currently encourages divers to bring their gear. Equipment can be rented at 2,50€/$3 USD per piece per dive.

Y-40: Maximum depth 42 m/138 ft

With an extra depth of 9 m/30 ft, Y-40 became the new record holder when it opened its doors in 2014. Its founder, Emanuele Boaretto, an architect, had dreamed about this project since the 1980s. In 2010, he finally went forward, assisted by scuba and freediving instructor Marco Mardollo. As for a venue, there was no better place than his family’s spa/hotel business; Y-40 is, indeed, part of the Hotel Terme Millepini, in Montegrotto Terme,  about 50 km/31 miles west of Venice.

While the pool surface has similar dimensions with 21 m/69 ft by 18 m/59 ft, Y-40’s pool has an internal volume of 4,135 m3/1,092,351 gallons which is 1.7 times bigger than Nemo 33 in Belgium. It features seven depth platforms at -1.3 m/-4 ft, -5 m/-16 ft, -6 m/-20 ft, -8 m/26 ft, -10 m/33 ft, -12 m/-39 ft, -15 m/-49 ft, and finally at the bottom of its shaft, -42.15 m/-138.3 ft. Its 13 m long transparent tunnel and its 60 m long underwater caves system make the pool a popular attraction for scuba divers coming from all over the world. But what makes Y-40 different, and still to this day, is its water. The spring water is naturally heated geothermically to a tropical temperature up to 34°C/93°F. 

Experience some deep joy at Y-40

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With more than a thousand scuba diving certifications per year, Y-40 prides itself on being the world’s largest dive center. However, over the years, Y-40 developed a strong reputation among the freediving community. Famous athletes like Alexey Molchanov, Guillaume Néry, and Herbert Nitsch, known for their depth records, have already visited the place. Y-40 can even count on Umberto Pelizzari; the freediving champion, known for his records in all the competitive apnea disciplines, is the president and founder of Y-40’s Apnea Academy.

On top of this, like most diving pools, they can cater to filming crews for underwater shooting and security professionals who need training, and they distinguish themselves in the field of scientific and medical hyperbaric studies. 

Since opening, the most important diving medicine centers from the United States, Europe, and South Africa have conducted experiments there. The distinguished list includes the DAN Europe Foundation, which led research with the University of Padua on the effects of depth on divers’ bodies and, more recently, the effects and risks of COVID-19 for divers

In 2021, Y-40 opened a medical surgery with doctors with diving expertise. They specialize in hyperbaric medicine, cardiology, neurology, nutrition, dentistry, and otolaryngology.

A dive at Y-40 for certified divers starts at 36€/$43.28USD during weekdays and 42€/$50.50USD during the weekend. The fins, the BCD, and the regulator are included in the fee. However, you need to bring your mask and dive computer (or rent them at 5€/$6USD for a mask and 10€/$12USD for a dive computer).

DeepSpot: Maximum depth 45 m/148 ft

The current record-holder for the deepest diving pool was opened at the end of 2020. Its founder is Michal Braszczynski, the owner of Aerotunel, a facility that simulates skydiving. 

Located in Mszczonów, about 50 km/31 miles south of Warsaw, the Deepspot pool has an impressive 8,000 m3/2,113,376 gallon internal volume of 33°C/91°F water. Like Y-40, it features a transparent tunnel suspended into the water and has a cave system for training in overhead environments.

Take a deep breath and Dive Into Deepspot

As of 2021, DeepSpot only offers recreational diving and freediving. Four in-house instructors teach a scuba diving and freediving course. And, five hotel rooms have an underwater window view of the pool. 

A dive at DeepSpot for certified divers starts at 189 zlotys (zł) (about 42€/$50.48USD) during weekdays and 219zł/49€/$58.89USD) during the weekend. All equipment is included in the fee, except for the dive computer. You can rent one at the cost of 30zł/7€/$8.41USD per dive. Accommodation in the underwater rooms is included in their Sleep & Dive packages, which start at 567zł/126€/$151.44USD per night.

Blue Abyss: Maximum depth 50 m/164 ft 

The Blue Abyss project aims to redefine a deep diving pool. While still in the planning phase, we have enough information to get excited about this new contender, which plans to open in 2023 in Newquay, Cornwall in the United Kingdom.

Its founder, John Vickers, a British army veteran and business consultant, launched the project in 2015. With the type of facility he had in mind (he knew even back then that he wanted to reach 50 m/164 ft and work with astronauts), there was no way this project was ever going to be straightforward. 

After the Blue Abyss team announced that the construction would begin in Colchester, then in Liverpool, the team finally decided to invest £150M/$210MUSD in the Cornish Aerohub Enterprise Zone near Newquay Airport to build the giant underwater facility. As announced in a press release on June 2, 2021, Blue Abyss is currently applying for a building permit, which should be completed by the end of the year; construction will take approximately 18 months.

The Blue Abyss diving pool is announced with a surface of 50 m/164 ft by 40 m/131 ft and a 42,000 m3/11,095,226 gallon internal volume, the equivalent of 17 Olympic swimming pools and more than five times bigger than Poland’s DeepSpot. With industrial and scientific users in mind, the pool will also be equipped with a sliding roof and a 30 tonne/33 ton crane to allow large objects to be lowered into the pool. 

Blue Abyss staff assure that recreational scuba divers, technical divers, and free divers will have ample access to the pool for training. However, the goal is to go beyond what publicly-accessible diving pools have ever achieved before.

The location, Cornwall, is strongly linked to the county’s dynamic aerospace and marine offshore energy industry. The connection to aerospace is so strong that  British astronaut Major Tim Peake sits on the Blue Abyss Advisory Board and acts as an ambassador of the project. 

A Few Honorable Mentions

  • SETT (Submarine Escape Training Tank) was the pool that inspired the creation of Nemo 33. Located in Portsmouth, UK, it was 30 m/98.4 ft deep and for military use only. It was a training facility used by the Royal Navy to teach soldiers to escape a disabled submarine. Opened after WWII, it just closed at the beginning of 2020.
  • While, technically, deep diving pools must reach a minimum depth of 30 m/98.4 ft to earn the title, it’s worth mentioning two diving pools in Asia, with K-26 in South Korea (26 m/85 ft deep) and DiveCube in Taiwan (21 m/69 ft deep). 
  • Not—strictly speaking—a pool, but you can dive in an old nuclear silo in Texas, USA, filled with 39 m/128 ft of water. 
  • France must have the greatest number of diving pools, with twelve 20 m/66 ft pools, five 15 m/49 ft pools, and four 12 m/39  ft pools, mostly built within France’s vast network of public swimming pools. 
  • In Belgium, Duiktank is a 15 m/49 ft pool in an old oil tank, and TODI is a 10 m/33 ft pool in an old coal mine in Belgium.

Dive Deeper:

InDepth: Deep Dive Dubai—The Deepest Pool In The World Is Not A Pool

Florine Quirion is a writer, underwater photographer, and a dive travel blogger at World Adventure Divers. She dives in tropical to extreme cold waters, and selects her destinations where adventurous diving and cultural discoveries are a part of the journey.

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Why It’s Okay To Make Mistakes

To err is human. To trimix is divine? Instructor evaluator Guy Shockey examines the importance of learning through one’s mistakes, and most important, being willing to admit and share them with others, especially for those in leadership positions. It’s the only way to create ‘psychological safety” within our community and improve our collective diving safety and performance. Wouldn’t that be divine?




By Guy Shockey. Images by Andrea Petersen

A few months back, I read an article about a club where members talked about failure and making mistakes. This club required that members freely discuss their mistakes and failures without fear of judgment. The goal was to destigmatize failure and recognize that we learn by making the very mistakes we are afraid to talk about! Moreover, to become truly high performing and develop unique and creative solutions to problems, the article argued that we needed to be free of the worry of failing—to understand that “to err is human.” 

The article went on to mention that for high performing teams to be successful, they needed to operate in an environment of “psychological safety.” This term was originally coined by Harvard professor Amy Edmondson, and Gareth Lock has written about the concept extensively. In his work with The Human Diver, Lock identifies psychological safety as a key component primarily missing in our diving culture. As a full-time diving professional and someone who delivers The Human Diver programs, I couldn’t help but reflect on the failure-destigmatizing club in the context of our diving culture in general and, more specifically, dive training.

Consider the humble Roomba robot vacuum cleaner. The Roomba learns how to clean a room by bumping into nearly everything in the room and, with some nifty software, creates a “map” of all the “vacuumable” space in the room. Then, it goes about its business efficiently and repetitively cleaning the room. The Roomba has learned by making multiple mistakes—much like humans do. 

Now imagine being able to transfer that new “map” from one Roomba to another so a new Roomba doesn’t have to repeat the mistakes of the first as it sets out to vacuum the room. Finally, imagine this transfer of data to be less-than-perfect—perhaps, occasionally, the new Roomba will make some mistakes (from which it will learn). But it will make far fewer mistakes than the original Roomba had to make. 

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I’m sure you can see where I’m going with this. Humans learn the same way Roomba vacuums do (hopefully without running into as many hard surfaces), and we can transfer information between each other. Because the transfer process is less than perfect, we still make some of the same old mistakes. This is particularly interesting because, despite drawing specific and repeated attention to these common errors, students often still make the same errors! One of the most important parts of instructor training is educating future instructors to recognize where these common mistakes will occur and encouraging them to ramp up to being hyper-vigilant rather than regular-vigilant. 

Learning Through Mistakes

One way we learn is by making mistakes, talking about them, and sharing the experience in the hopes that future divers don’t have to make the same ones. At its core, this is the very essence of learning. Incidentally, this is also what makes experience such an important characteristic of a good teacher. The more experience the educator has, the more mistakes they’ve made and, consequently, the more information they can transfer. Fear of owning our mistakes keeps us from learning from them; perhaps more importantly, it means that others will miss out on these important lessons. 

Yet, in diving culture, we (for the most part) shy away from discussing the mistakes and errors we (hopefully) learned from for fear of being considered a less than capable diver. When divers in influential or leadership roles do this, it is a tremendous loss for the diving community in general—it robs future groups of divers of the opportunity to learn. Sadly, because this commonly happens at the leadership level, it is hardly surprising that other divers further down the line copy that behavior, and we ultimately end up with a diving culture that emulates the example of the leadership. 

I advocate for taking the opposite approach. In my teaching, I am very open about the mistakes or errors I have made while diving. I recognize that I am basically a smart Roomba, and I learn by making mistakes. Thus, it would be disingenuous to pretend that I don’t make mistakes—I had to learn somewhere! I believe this approach lends authenticity to my instruction and starts to create psychological safety in my classes. Ultimately, my goal is to encourage students to recognize that, “If the instructor can admit they make mistakes, then it is okay to talk about the ones our team made during the training dive.” 

I have found that there is a remarkable change in the relationship between student and instructor when this happens. Learning becomes more of a collegial activity, and stress and performance anxiety significantly decrease. This leads to more successful learning outcomes and happier students. I am a firm believer that, while training can be serious, it should also be fun!

Creating Psychological Safety

Creating psychological safety in our diving culture is a daunting task, but every flood begins with a single raindrop. The first thing that needs to happen—at all levels—is an acknowledgement of failures and mistakes among  those in positions of influence and leadership. Sadly, this is not as easy as it sounds, and there is frequent pushback. Ego is one of the most dangerous aspects of a personality and it frequently causes people to overreach, crippling growth and learning. The irony here is that every single one of us has made a mistake. We all understand that no one is perfect, yet many in leadership positions cling to the view that vulnerability is weakness—that demonstrating imperfection will cause others to stop trusting them (or revering them). 

I propose that the opposite is true. I should also note that I believe every dive professional is acting in a leadership role. This means that, while creating psychological safety can best be started by those in senior leadership roles, it must also be encouraged at all levels of leadership, including anyone in supervisory or teaching roles. In a perfect world, every diver would embrace this approach and enable psychological safety within their team.

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There are a few things you can do to help develop psychological safety. First, facilitate a debrief at the end of the dive and begin with “something that I as the leader did wrong or could have done better was…” This immediately creates fertile soil for psychological safety to flourish. When the leader is the first person to say, “I made a mistake,” it establishes that this is a safe place to discuss mistakes and errors with the intention of learning from them. This opens the door to follow-up discussions. 

On the subject of transparency, in any organization it is often the voice of dissent—a contrary position—that is the most valuable. This voice causes the group to reflect on original assumptions and decisions and offer a perspective that “groupthink” does not. This means that we need to be open to different solutions to problems lest we be blinded by our own cognitive biases—ones that have been developed over thousands of years of evolution in order to make us more efficient Roombas. 

We are essentially fighting against our own brains, and it takes a significant amount of effort to think outside the box. We are hard-wired to think in terms of “evolutionary” rather than “revolutionary” ideas, and we need to make a conscious effort to consider the voice of dissent and understand why it is so hard to do so. 

In Conclusion

In psychologically safe environments, we experience a significant increase in “discretionary effort,” or shifts on the “need to do” and the “want to do” curves. If a team has a high degree of psychological safety, they are motivated to perform higher than the minimum standard. If you create a high degree of psychological safety, your team will perform better as a result. 

This is where it all comes full circle. We want our dive teams to perform at a high level. We want them to have a high degree of discretionary effort. We want them to embrace our “commitment to excellence.” Therefore, we must be the ones to create the psychological safety necessary to facilitate this growth. 

One of the most effective things you can do as a leader is to be open and willing to share that, in the end, you are human too. You make mistakes, you admit to them, you learn from them, and you share them with others so they can learn too.

One of the most effective things you can do as a leader is to be open and willing to share that, in the end, you are human too. You make mistakes, you admit to them, you learn from them, and you share them with others so they can learn too.


Other stories by Guy Shockey:

InDEPTH: Reflections on Twenty Years of Excellence: Holding The Line (2019)

InDEPTH: Situational Awareness and Decision Making in Diving (2020)

InDEPTH: The Flexibility of Standard Operating Procedures (2021)

InDEPTH: How to Become an Explorer: Passion, Partnership, and Exploration (2022)

InDEPTH: Errors In Diving Can Be Useful For Learning— ‘Human Error’ Is Not! by Gareth Lock

InDEPTH: Learning from Others’ Mistakes: The Power of Context-Rich “Second” Stories by Gareth Lock

Guy Shockey is a GUE instructor and instructor trainer who is actively involved in mentoring the next generation of GUE divers. He started diving in 1982 in a cold mountain lake in Alberta, Canada. Since then, he has logged somewhere close to 8,000 dives in most of the world’s oceans. He is a passionate technical diver with a particular interest in deeper ocean wreck diving. He is a former military officer and professional hunter with both bachelor’s and master’s degrees in political science. He is also an entrepreneur with several successful startup companies to his credit.

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