Y-40 The Deep Joy, Montegrotto Terme · 몬테그로토 테르메 (파도바)
Location
Overview
Less than an hour from Venice, in the spa town of Montegrotto Terme, the Hotel Terme Millepini houses an indoor diving pool that drops to 42.15 m. The surface is only 21x18 m, but below it sit stepped platforms and a cylindrical vertical well, filled with 4.3 million litres of salsobromoiodic thermal water held at 32-34°C year round. No swell, no current, no thermocline, and visibility that runs the length of the pool, which is why European freedivers come here in winter to rebuild equalisation and clean up their freefall. It was the deepest pool in the world when it opened in 2014; today it ranks third behind Deep Dive Dubai (60 m) and Poland's Deepspot (45.45 m), while keeping the Guinness record for the deepest thermal-water pool.
The vertical well and its descent line, the reason most freedivers come: 42 m of uninterrupted line for drilling mouthfill and freefall position
Stepped platforms at intermediate depths, used for warm-ups, shallow skills work and instructor feedback
Roughly 60 m of underwater caves built for cave-diving instruction, worth seeing from outside and worth respecting as a genuine overhead environment
The transparent viewing tunnel, where non-divers can watch the sessions, and the filming conditions that have made the pool a regular set for underwater video and art films
Winter workshop season, when mouthfill and deep-technique clinics led by names such as Umberto Pelizzari and Giovanni Bianco fill the calendar
Good to know
SafetyDo not let the word 'pool' soften this. 42 m is real deep diving, and hypoxic blackout remains the leading cause of freediving deaths. The danger zone is not the bottom but the last 10 m of ascent and the moments at the surface, which is why Y-40's own rules require the surface partner to meet the ascending diver from one third of the maximum depth. Keep eyes on your buddy for at least 30 seconds after they surface.
SafetyWater at 32-34°C is comfortable but physiologically unhelpful. The bradycardia of the dive response is blunted in warm water compared with cold, and overheating plus dehydration push oxygen consumption up. Research on deep-pool diving has also documented hypoxia developing at depth through atelectasis and ventilation-perfusion mismatch. Personal bests set in cold open water do not transfer here.
RulesA lanyard is mandatory to enter the well, whatever depth you plan to reach. Every diver must carry their own freediving computer, and staff must be able to read the depth and time log from it. Diving without a certified buddy or an instructor is not permitted; if you arrive alone, book a session with Y-40 safety or trainer cover instead.
SafetyThe caves and tunnels are an overhead environment. If something goes wrong there is no direct route to the surface. Freedivers without specific cave training should stay out entirely, including the 'just a look at the entrance' version of the idea.
RulesThe admin is strict. You must create a Y-40 account, upload a photo of your ID, sign the regulations and complete online check-in, with arrival recommended 60 minutes before the slot. Trainer sessions, courses and workshops require a sports medical certificate with ECG, and the Pelizzari workshop requires the competitive-grade certificate. Minors need an accompanying adult and are held to age-based depth caps, so confirm the current conditions before booking.
SeasonThe pool is indoor and thermal, so it runs all year, but line time is not unlimited. Sessions are capped in numbers and shared with scuba groups, which can shorten your time on the descent line. Winter and workshop weeks are the busiest, so book as soon as your dates are fixed.
MannersOne line, many divers. Respect the alternating rotation, do not monopolise the rope, and leave the hyperventilation and packing displays at home. Treat staff instructions as regulations rather than suggestions.
Practical info
Venice Marco Polo airport is roughly 40-50 minutes by car, Padua about 20, and Montegrotto Terme has its own railway station within easy reach of the site. Many freedivers simply stay at Hotel Terme Millepini and train in the same building. Tickets range from the standard entry for certified divers to safety-supervised sessions, trainer sessions and memberships, all on booked slots, so check the official site for current prices, opening hours and required paperwork before you commit.
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