SM U - 30 ( Austria - Hungary ) SM " U - 30 or U - XXX " was a " U - 27 " class U - boat or submarine of the Austro - Hungarian Navy . " U - 30 " , built by the Hungarian firm of Ganz Danubius at Fiume , was launched in December 1916 and commissioned in February 1917 . " U - 30 " had a single hull and was just over in length . She displaced nearly when surfaced and over when submerged . Her two diesel engines moved her at up to on the surface , while her twin electric motors propelled her at up to while underwater . She was armed with two bow torpedo tube s and could carry a load of up to four torpedoes . She was also equipped with a deck gun and a machine gun . " U - 30 " sank no ships during her brief service career . She departed from Cattaro on 31 March 1917 and was never heard from again . She may have succumbed to a mine in the Otranto Barrage but her fate remains a mystery . Design and construction . Austria - Hungary ' s U - boat fleet was largely obsolete at the outbreak of World War I . The Austro - Hungarian Navy satisfied its most urgent needs by purchasing five Type UB I submarines that comprised the from Germany , by raising and recommissioning the sunken French submarine " Curie " as , and by building four submarines of the that were based on the 1911 Danish " Havmanden " class . After these steps alleviated their most urgent needs , the Austro - Hungarian Navy selected the German Type UB II design for its newest submarines in mid 1915 . The Germans were reluctant to allocate any of their wartime resources to Austro - Hungarian construction , but were willing to sell plans for up to six of the UB II boats to be constructed under license in Austria - Hungary . The Navy agreed to the proposal and purchased the plans from AG Weser of Bremen . " U - 30 " displaced surfaced and submerged . She had a single hull with saddle tank s , and was long with a beam of and a draft of . For propulsion , she had two shafts , twin diesel engines of for surface running , and twin electric motors of for submerged travel . She was capable of while surfaced and while submerged . Although there is no specific notation of a range for " U - 30 " in " Conway ' s All the World ' s Fighting Ships , 1906 – 1921 " , the German UB II boats , upon which the " U - 27 " class was based , had a range of over at surfaced , and at submerged . " U - 27 " - class boats were designed for a crew of 23 – 24 . " U - 30 " was armed with two bow torpedo tube s and could carry a complement of four torpedoes . She was also equipped with a 75 mm / 26 ( 3 . 0 in ) deck gun and an machine gun . After intricate political negotiations to allocate production of the class between Austrian and Hungarian firms , " U - 27 " was ordered from Ganz Danubius on 12 October 1915 . She was laid down on 9 March 1916 at Fiume and launched on 27 December . Service career . " U - 30 " began diving trials on 8 January 1917 , and made her first underwater cruise on 27 January . On 1 February , she successfully reached a depth of in compression tests . Four days later she took on a crew for a training voyage , and made her way to Pola . At that port , on 21 January 1917 , SM " U - 30 " was commissioned into the Austro - Hungarian Navy under the command of " Linienschiffsleutnant " Friedrich Fähndrich . Fähndrich , a 29 - year - old native of Budapest , had previously served as commander of . " U - 30 " departed on her first patrol on 26 February , for duty off Cape Matapan and the Gulf of Taranto . During the patrol , " U - 30 " did not encounter any hostile ships , but did encounter a storm that caused extensive damage . Cutting short her cruise with damage to the parapet on her conning tower , a missing radio aerial , and a broken gyrocompass , " U - 30 " arrived in Cattaro on 16 March for repairs . With the repairs complete , " U - 30 " set out from Cattaro on 31 March and was never heard from again . Author Paul Halpern suggests that a mine in the Otranto Barrage might have been responsible . Authors R . H . Gibson and Maurice Prendergast report that there is no evidence in Allied records to indicate the possible fate of the U - boat , and conclude that the fate of " U - 30 " remains a mystery , and " is likely to remain so for ever " . " U - 30 " was not credited with the sinking of any ships in her brief career . She was also the only member of the " U - 27 " - class to be lost during the war .