the Acheron Project Pty Ltd, has reached Challenger Deep, the world's deepest seabed. Limiting Factor A submersible commissioned by Caladan Oceanic and designed and built by Triton Submarines of Sebastian, Florida. On December 19, 2018 it was the first crewed submersible to reach the bottom of the Atlantic Ocean, or 8,376 meters in the Brownson Deep, thus making it the deepest diving, currently operational submersible. In August 2019, the submersible and its pilot, Victor Vescovo, completed the "Five Deeps Expedition" with its support ship, the DSSV Pressure Drop, becoming the first submersible to visit the bottom of all five of the world's oceans. Earlier that same month, a team of explorers and scientists used Limiting Factor to visit the wreck of the RMS Titanic in the North Atlantic Ocean. On March 31, 2021, Caladan Oceanic announced having re-located, surveyed, and filmed the wreck of the World War II destroyer , sunk on October 25, 1944, in the Battle off Samar (in the Philippine Sea off Samar Island). Johnston lies at depth of , making Limiting Factors expedition the deepest wreck dive in history. Priz-class DSRV Priz a DSRV class of five ships built by the USSR and Russia. The titanium-hulled Priz class are capable of diving to . These mini-submarines can ferry up to 20 people for very brief periods of time (in case of a rescue mission) or operate submerged for two to three days with a regular crew of three to four specialists. In early 2005, the Russian AS-28 Priz vessel was trapped undersea and subsequently freed by a British ROV in a successful international rescue effort. Mir Mir a strictly civilian (research) class of two DSVs which were manufactured in Finland for the USSR. These bathyscaphe-derived vessels can carry three people down to depths of . After visiting and filming the RMS Titanic's wreck, the two Mir submersibles and their support ship were loaned to a US Pacific trench surveying mission in the late 1990s and made important discoveries concerning sulphuric based life in "black smokers". Kalitka-class DSVN AS-12 a Russian counterpart to the American NR-1 clandestine nuclear DSV, is a relatively large, deep-diving nuclear submarine of 2,000 tons submerged displacement that is intended for oceanographic research and clandestine missions. It has a titanium pressure hull consisting of several conjoined spheres and able to withstand tremendous pressure — during the 2012 research mission it routinely dove to