Nemo 33 was the deepest indoor swimming pool in the world before Y-40 in Montegrotto Terme, Padua, Italy was completed. The pool is located in Brussels, Belgium. Its maximum depth is 34.5 metres (113 ft). It contains 2,500,000 litres (550,000 imp gal; 660,000 US gal) of non-chlorinated, highly filtered spring water maintained at 30 °C (86 °F) and holds several simulated underwater caves at the 10 metres (33 ft) depth level. Due to the warm temperature in the pool, divers can dive for extended periods without a wet suit. [Wikipedia]
Y-40, a brand new paradise for scuba and free divers of all levels opens its depths on Saturday, May 10, 2014. It was endowed with a name Y-40 and with its „-40“ meters (-131 feet), it becomes the single deepest pool ever built in the world. The Italians have actually added 7 meters, beating the existing Belgian record holder Nemo 33, which also bears the depth dimension in its name. The deepest pool of all times enters the world´s diving stage and also the Guinness World Records.
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