SM U - 20 ( Austria - Hungary ) SM " U - 20 or U - XX " was the lead boat of the of submarine s or U - boat s built for and operated by the Austro - Hungarian Navy ( ) during the First World War . The design for " U - 20 " was based on submarines of the Royal Danish Navy ' s " Havmanden " class ( three of which had been built in Austria - Hungary ) , and was largely obsolete by the beginning of the war . " U - 20 " was just over long and was armed with two bow torpedo tubes , a deck gun , and a machine gun . " U - 20 " had no wartime successes and was sunk in early July 1918 by the Italian submarine " F - 12 " . The wreck of " U - 20 " was located in 1962 and salvaged . A portion of her conning tower is on display in a military museum in Vienna . Design and construction . When it became apparent to the Austro - Hungarian Navy that the First World War would not be a short war , they moved to bolster their U - boat fleet by seizing the plans for Denmark ' s " Havmanden " class submarines , three of which had been built at Whitehead & Co . in Fiume . Although the Austro - Hungarian Navy was not happy with the design , which was largely obsolete , it was the only design for which plans were available and which could be begun immediately in domestic shipyards . The Austro - Hungarian Navy unenthusiastically placed orders for " U - 20 " and her three sister boats on 27 March 1915 . " U - 20 " was one of two boats of the class to be built at the Pola Navy Yard . Due to demands by the Hungarian government , subcontracts for the class were divided between Hungarian and Austrian firms , but this politically expedient solution worsened technical problems with the design and resulted in numerous modifications and delays for the class in general . " U - 20 " was an ocean - going submarine that displaced surfaced and submerged and was designed for a complement of 18 . She was long with a beam of and a draft of . For propulsion , she featured a single propeller shaft , a single diesel engine for surface running , and a single electric motor for submerged travel . She was capable of while surfaced and while submerged . Although there is no specific notation of a range for " U - 20 " , the " Havmanden " class , upon which the " U - 20 " class was based , had a range of at , surfaced , and at submerged . " U - 20 " was armed with two torpedo tubes located in the front and carried a complement of two torpedoes . She was also equipped with a 66 mm / 26 ( 2 . 6 in ) deck gun and an machine gun . " U - 20 " was laid down on 29 September 1915 , six months after she was ordered , and was launched on 18 September 1916 . Service career . Upon completion , " U - 20 " began diving trials . On her 15 March 1917 trial , she was accidentally rammed by in the Fasana Channel . The collision with the Austro - Hungarian light cruiser twisted " U - 20 " s periscope , extensively damaged the conning tower , and knocked off her deck gun . After seven months of reconstruction , " U - 20 " was commissioned into the Austro - Hungarian Navy on 20 October . After initially operating out of Pola , " U - 20 " was transferred to Trieste in February 1918 . Over the next three months , the U - boat patrolled in the northern Adriatic between the Tagliamento estuary and Venice . " U - 20 " had an encounter with an enemy submarine on 7 April but was not able to successfully launch an attack . On 3 July , " Linienschiffsleutnant " Ludwig Müller sailed " U - 20 " out from Trieste for the Gulf of Venice . A day later , " U - 20 " was spotted by the Italian submarine " F - 12 " , which was on patrol in the northern Adriatic . " F - 12 " initially pursued " U - 20 " underwater , and then on the surface . At a range of , " F - 12 " torpedoed " U - 20 " at position , sinking her with all hands . There was no wreckage on the surface , only an oil slick . Like all of her sister boats , " U - 20 " had no wartime successes . In mid 1962 , the wreck of " U - 20 " was discovered in the northern Adriatic . Italian salvage crews raised the boat ' s rear portion on 22 July and her front section on 21 November . The conning tower and a small midships section of " U - 20 " were donated to the Heeresgeschichtliches Museum in Vienna , where they are on display , while the rest of the boat was scrapped . The remains of the crewmen were buried on the grounds of the Theresian Military Academy at Wiener Neustadt .