Bathyscaphe Trieste Trieste is a Swiss - designed , Italian - built deep - diving research bathyscaphe , which with her 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 achieving the goal of Project Nekton . " Trieste " was the first manned vessel to have reached the bottom of the Challenger Deep . Design . " Trieste " consisted of a float chamber filled with gasoline ( petrol ) for buoyancy , with a separate pressure sphere to hold the crew . This configuration ( dubbed a " bathyscaphe " by the Piccards ) , allowed for a free dive , rather than the previous bathysphere designs in which a sphere was lowered to depth and raised from a ship by cable . " Trieste " was designed by the Swiss scientist Auguste Piccard and originally built in Italy . His pressure sphere , composed of two sections , was built by the company Acciaierie Terni . The upper part was manufactured by the company Cantieri Riuniti dell ' Adriatico , in the Free Territory of Trieste ( on the border between Italy and Yugoslavia ) ; hence the name chosen for the bathyscaphe . The installation of the pressure sphere was done in the Cantiere navale di Castellammare di Stabia , near Naples . " Trieste " was launched on 26 August 1953 into the Mediterranean Sea near the Isle of Capri . The design was based on previous experience with the bathyscaphe " FNRS - 2 " . " Trieste " was operated by the French Navy . After several years of operation in the Mediterranean Sea , the " Trieste " was purchased by the United States Navy in 1958 for $ 250 , 000 . At the time of " Project Nekton " , the " Trieste " was more than 15 m ( 50 ft ) long . The majority of this was a series of floats filled with of gasoline , and water ballast tanks were included at either end of the vessel , as well as releasable iron ballast in two conical hoppers along the bottom , fore and aft of the crew sphere . The crew occupied the 2 . 16 m ( 7 . 09 ft ) pressure sphere , attached to the underside of the float and accessed from the deck of the vessel by a vertical shaft that penetrated the float and continued down to the sphere hatch . The pressure sphere provided just enough room for two people . It provided completely independent life support , with a closed - circuit rebreather system similar to that used in modern spacecraft and spacesuits : oxygen was provided from pressure cylinders , and carbon dioxide was scrubbed from breathing air by being passed through canisters of soda - lime . Power was provided by batteries . The " Trieste " was subsequently fitted with a new pressure sphere , manufactured by the Krupp Steel Works of Essen , Germany , in three finely - machined sections ( an equatorial ring and two caps ) . To withstand the enormous pressure of 1 . 25 tonne per cm² ( 110 MPa ) at the bottom of Challenger Deep , the sphere ' s walls were thick ( it was overdesigned to withstand considerably more than the rated pressure ) . The sphere weighed 13 metric tons in air and eight metric tons in water ( giving it an average specific gravity of 13 / ( 13 - 8 ) = 2 . 6 times that of sea water ) . The float was necessary because of the sphere ' s density : it was not possible to design a sphere large enough to hold a person that could withstand the necessary pressures , yet also have metal walls thin enough for the sphere to be neutrally buoyant . Gasoline was chosen as the float fluid because it is less dense than water , incompressible even at extreme pressure , thus retaining its buoyant properties and negating the need for thick , heavy walls for the float chamber . Observation of the sea outside the craft was conducted directly by eye , via a single , very tapered , cone - shaped block of acrylic glass ( Plexiglas ) , the only transparent substance identified which would withstand the external pressure . Outside illumination for the craft was provided by quartz arc - light bulbs , which proved to be able to withstand the over 1 , 000 atmospheres of pressure without any modification . Nine tons of magnetic iron pellets were placed on the craft as ballast , both to speed the descent and allow ascent , since the extreme water pressures would not have permitted compressed air ballast - expulsion tanks to be used at great depths . This additional weight was held in place at the throats of two hopper - like ballast silos by electromagnets , so in case of an electrical failure the bathyscaphe would automatically rise to the surface . Transported to the Naval Electronics Laboratory ' s facility in San Diego , California , " Trieste " was modified extensively by the Americans , and then used in a series of deep - submergence tests in the Pacific Ocean during the next few years , culminating in the dive to the bottom of the Challenger Deep during January 1960 . The Mariana Trench dives . " Trieste " departed San Diego on 5 October 1959 for Guam aboard the freighter " Santa Maria " to participate in " Project Nekton " , a series of very deep dives in the Mariana Trench . 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 . The descent to the ocean floor took 4 hours 47 minutes at a descent rate of . After passing one of the outer Plexiglas window panes cracked , shaking the entire vessel . The two men spent barely twenty minutes on the ocean floor , eating chocolate bars for sustenance . The temperature in the cabin was 7 °C ( 45 °F ) at the time . While at maximum depth , Piccard and Walsh unexpectedly regained the ability to communicate with the support ship , USS " Wandank " ( ATA - 204 ) , using a sonar / hydrophone voice communications system . At a speed of almost a mile per second ( about five times the speed of sound in air ) , it took about seven seconds for a voice message to travel from the craft to the support ship and another seven seconds for answers to return . While at the bottom , Piccard and Walsh observed a number of small sole and flounder . Their claim the fish were swimming would prove at least some vertebrate life can withstand the extreme pressure at the oceans ' deepest point . They noted that the floor of the Challenger Deep consisted of " diatom aceous ooze " . The ascent took 3 hours 15 minutes . Other deep dives by " Trieste " . Beginning in April 1963 , " Trieste " was modified and used in the Atlantic Ocean to search for the missing submarine . " Trieste " was delivered to Boston Harbor by USS " Point Defiance " ( LSD - 31 ) under the command of Captain H . H . Haisten . In August 1963 , " Trieste " found the wreck off the coast of New England , below the surface . " Trieste " was changed , improved and redesigned so many times that almost no original parts remain . She was transported to the Washington Navy Yard where she was exhibited along with the Krupp pressure sphere in the National Museum of the U . S . Navy at the Washington Navy Yard in 1980 . Her original Terni pressure sphere was incorporated into the " Trieste II " . In art and literature . The song ' The Trench ' by Danish composer Ste van Holm is a tribute to the Mariana Trench dives . " Voyage Of The Trieste " - an instrumental track on The Chocolate Watchband ' s 1968 LP " The Inner Mystique " . " Trieste " figures prominently in the 2008 novel " The Extraordinary Event of Pia H . " by Canadian writer Nicola Vulpe .