Bathyscaphe Trieste
Trieste is a Swiss-designed, Italian-built deep-diving research bathyscaphe, which with its crew of two reached a record maximum depth of about , in the deepest known part of the Earth's oceans, the Challenger Deep, in the Mariana Trench near Guam in the Pacific. On 23 January 1960, Jacques Piccard (son of the boat's designer Auguste Piccard) and US Navy Lieutenant Don Walsh achieved the goal of Project Nekton.
Hranice Abyss
The Hranice Abyss (), the English name adopted by the local tourist authorities, is the deepest flooded pit cave in the world. It is a karst sinkhole located near the town of Hranice (Přerov District). The greatest confirmed depth (as of 27 September 2016) is 473 m (404 m under the water level), which makes it the deepest known underwater cave in the world. Moreover, the expected depth is 800–1200 m.