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HomeFreedivingVisiting the Y-40 - The World's Deepest Pool

Visiting the Y-40 – The World’s Deepest Pool

The world’s deepest pool, and it is hard to call it simply a pool, is located in the area of Padova, North East of Italy – in the town of Montegrotto Terme. Y-40 opened in June 2014 and since then has started attracting divers from all over the World.  I had the great opportunity to attend an event at the facility along with a number of Freediving and Spearfishing legends such as Umberto Pelizzari, Herbet Nitsch, Andrea Zuccari, Ilaria Molinari, Ilaria Bonin, Cico Nat, Marco Bardi and Stefano Claut.

The Design Of The Y-40

Surface area of the pool is 21×18 meters, maximum depth is -40 meters / 131 feet, with various intermediary depths. The structure is incredibly refined and wide lateral windows permit sunlight to illuminate the whole pool increasing visibility in the water which, thanks to its natural transparency, reaches up to 60 meters. The swimming pool contains 4300 cm of water kept at a temperature of 33.3 Celsius / 92 Fahrenheit. Since thermal water is naturally at the very high temperature of 87°C, and it is used for thermal therapy at 36°C, the water for the pool is actually cooled down making it pass along a system of external passages. 33,3°C are the perfect temperature for diving, which means slow and minimal movements during the preparation and diving phases. It would not of course work as temperature to swim in, as it would be too hot, but this is not the case.


The pool is completed by a number of caves that are used for specific training, while a central transparent tunnel is a passage for people outside the pool, which makes it possible to watch divers and champions move, practice and dive in the pool.


The entire structure is built just near the Hotel Millepini, which works as a perfect base, as it also has thermal areas to enjoy.

What it means to dive in Y-40

With my visit, I could not resist a test dive in such an incredible pool. It is strange and exiting to prepare for a dive without wearing wetsuit, weights, gloves and any heavy and compelling equipment. The internal environment of the pool is warm already outside the water. When entering with just your costume, fins and mask, you feel extremely free, and sensation taking contact with the 33,3 °C water is of particular pleasure and comfort.

Open Day starts

A number of buoys are in the water indicating different depths. They are connected to the bottom of the pool through lines, which are sufficiently tense so to be able to hold to them while starting the preparation of the dive. This moment is incredible, the relaxation obtainable dew to the water temperature, the absence of waves and the visibility underwater, gives a sense of calm and peace, most probably bringing us back with very similar conditions we once lived in our mother’s womb. All the ventilation process is carried out with a never before experienced ease. With extreme calm, I dived to 10, 15, 20, 25 and 30 meters. The action was easy and fluid, the first dives down to 15 meters were done on the shallow water platforms, while from 20 meters on I moved to the heart of the pool, with its 40 meters deep cylindrical structure. This had three tough and tense ropes positioned in a triangle coming down from the ceiling to the bottom at -40 meters. The ropes from the ceiling where then connected to a blocking system, one for each rope. Such system is actually a security solution that permits, connecting the diver with the ropes, to bring him/her up from underwater in case of any possible critical situation. Such ropes are also a point of reference for the divers during the dive, so they can follow a straight vertical line, just as the divers in official apnea dives tests.

When entering the cylindrical part of the pool in the -40 area, depth is easily visible thanks to a vertical graduated scale. Dives to -25 and -30 meters where more challenging, but still extremely comfortable and not at all requesting me reaching my limit. Still, at -30 meters, even though the whole situation really gives extreme comfort and capacity of going beyond ones traditional limits in the sea, I rationally decided to stop my dives, also considering my lack of proper preparation yet this year.


In conclusion, experience is particularly impressive, sensation is that one would really never exit the pool, but my mission called me back to reality and I started my interview with the one of the founder, and current manager of Y-40, Marco Mardollo. Morning Mr. Mardollo, how did it all start, when did the idea of a -40 meters pool come to your mind?

Marco Mardollo: It was almost 15 years ago when the son of the owner of the Millepini Hotel, Emanuele Boaretto, talked to me, as expert Apnea Academy instructor, about his wish to build a swimming pool in an area just near the Hotel, where there was a ruin and where it was possible to build. Years have passed by since then with no real final decision, until three years ago, when we decided that the area of Montegrotto Terme could not live only of thermal therapy offer, but needed some strong and unique solution that would catalyze tourists, possibly bringing younger people to us.

Emanuele Boaretto is a skilled architect and has designed completely the new structure of Y-40, following directly all the works, which started June 2013. After one year Y-40 was born.

DB: How did you define all the practical solutions and details of the pool?

MM: Many ideas have come from focus groups we have set up, both with expert instructors and diving champions, but also with Apnea Academy students. Many ideas and solutions for the optimization of the pool have been defined and applied through these focus groups. An example is to have music in the pool, which is an additional support to relaxation and concentration.

DB: How has Y-40 been welcomed by divers?

MM: We have done no real communication of the pool on a pure advertisement side, but as soon as people came to hear about the structure, reaction was immediate. Moreover, whoever comes to visit us and dives in Y-40 always wants to come back, and, actually, they really never want to come out of the water!

DB: Which are the plus of Y-40?

MM: Well, first of all of course the fact that it is unique around the World, in addition it is a very high quality structure, built with top quality materials and solutions, and, as already commented, following the ideas and opinions of people fully involved in diving, both freeding and scuba diving. But this is not all: thermal structure of Hotel Millepini are surely an additional attraction, also giving possibility for couples who do not both dive, to have the opportunity of diving, but also of a relaxing and healthy thermal treatment. Moreover, Venice is just 40 minutes away. What else could one ask?

DB: From which countries do your guests come from and what kind of guests do you have?

MM: Of course Italy, but many from Germany, Austria, Europe eastern countries, Asia. Americans also come from the US Army in Vicenza. Guests are also companies who like doing teamwork using our pool, which, by the way, is complete with meeting rooms, for 40, 60 and 100 people.

DB: What kind of courses are done in Y-40?

MM: Any kind of course, from basic to advanced to instructor courses, from freediving to scuba diving, but also courses such as cave dives, thanks to the presence of caves in the pool, designed by the cave diving instructor Gigi Casati.

DB: Any kind of interesting event done?

MM: Apart from today’s event, organized by Apnea Academy and Omer, which puts together incredible champions, such as Umberto Pelizzari, Herbet Nitsch, Andrea Zuccari, Ilaria Molinari, Ilaria Bonin, Cico Nat, Marco Bardi and Stefano Claut, which has attracted an incredible number of enthusiasts, we have done an interesting and innovative event for the Padova bicycle event, Expo Bici. This show will be held in Padova this September and we have shot a video with a cycler moving underwater with his bicycle, going from the top down to -10, -15 meters and then down to – 40 meters, of course with a balloon to reduce vertical speed and final impact. The video, that you can see below, has come out really well and will be used to promote the Expo Bici:

A chat with Umberto Pelizzari

We also met Umberto Pelizzari at the Y-40 event, one of the most charismatic and well known of all freediving champions around the world. Although now 50 years old, looking at his physique you would advise freediving as solution for eternal youth to all. Umberto is the man who has actually managed to put together so many champions in one single event.

nodrugscampaignbyapneaacademy Umberto, a comment on Y-40.

Umberto Pelizzari: Y-40 is unique, and creates fantastic situations, thanks to the optimal temperature, the tranquility and secureness sensation you have in the pool. The absence of wetsuit gives you much better feel and awareness of your body. Especially in cold periods, Y-40 is a real point of reference for training and well being.

DB: You have indicated the advantages of Y-40, which are the limits?

UP: For sure you cannot go deeper then -40 meters! The sea of course can give, especially to the more trained and to the champions, the possibility to go much deeper. Still, you can train in Y-40 using some technical adaptations; for example not filling your lungs completely to challenge yourself in -40 meters as if they were more.

DB: This year you are celebrating 20 years anniversary of Apnea Academy, a great result and goal. A comment?

UP: The first idea came in ’95 , when there was really little academy on diving, and we decided to fill the gap. Freediving was brought forward by enthusiasts automatically, with no real notion on fundamental aspects like, for example, equalization. Champions like Enzo Maiorca have reached incredible depth with no real advanced technique, but only their natural predisposition to freediving. Experts like Andrea Zuccari have studied equalization techniques and have evolved freediving to what it is today. I, myself, have learned a lot on the equalization technique from Andrea. Since ’95 didactics has been created, a great goal.

DB: A comment on spearfishing

UP: I love spearfishing, especially deep fishing catching snappers. I usually fish between North of Sardegna and Corsica. I am only sorry that many areas are being closed to fishing and especially spearfishing, which is instead, a very respectful way of catching fish, of course always meant to eat it. There should be more knowledge and real interest by politicians and institutions to regulate fishing and spearfishing without though prohibiting to live a beautiful sport.

ZuccariPellizzariNitschTo find out more about the Y-40 and plan your diving there head to

Carlo Forni
Carlo Forni
43 years old, living between Rome and Sardinia island, Italy, Carlo is a journalist and mechanical engineer. His greatest passion is the sea, without which he says he could not live. He practices spearfishing since the age of 14. Frequent fishing areas are the Mediterranean, in particular the island of Sardinia, Lazio and Tuscany coasts (including Giglio and Ponza islands).