 U @-@ 3 was authorized in 1906 , begun in March 1907 , launched in August 1908 , and towed from Kiel to Pola in January 1909 . The double @-@ <unk> submarine was just under 139 feet ( 42 m ) long and displaced between 240 and 300 tonnes ( 260 and 330 short tons ) , depending on whether surfaced or submerged . The design of the submarine had poor diving qualities and several modifications to U @-@ 3 's diving planes and fins occurred in her first years in the Austro @-@ Hungarian Navy . Her armament , as built , consisted of two bow torpedo tubes with a supply of three torpedoes , but was supplemented with a deck gun in 1915 . 
