Bathyscaphe Trieste
On 23 January 1960, she reached the ocean floor in the Challenger Deep (the deepest southern part of the Mariana Trench), carrying Jacques Piccard and Don Walsh. This was the first time a vessel, manned or unmanned, had reached the deepest known point of the Earth's oceans. The onboard systems indicated a depth of , although this was revised later to ; fairly recently, more accurate measurements have found Challenger Deep to be between and deep.
Hotel Terme Millepini
Y-40 "The Deep Joy" pool first opened on 5 June 2014 and was designed by architect Emanuele Boaretto. It is deep, making it the deepest pool in the world. It contains 
of thermal water kept at a temperature of . The pool features underwater caves and a suspended, transparent, underwater tunnel for guests to walk through. It includes platforms at various depths, ranging from to , before the walls of the pool narrow into a well-like funnel which plunges straight down to . The hotel offers tickets to freedive and scuba dive. Italian freediver Umberto Pelizzari first measured the depth before the pool was open.