SM UB - 3 SM " UB - 3 " was a German Type UB I submarine or U - boat in the German Imperial Navy ( ) during World War I . She disappeared on her first patrol in May 1915 , and was the first of her class to be lost . " UB - 3 " was ordered in October 1914 and was laid down at the Germaniawerft shipyard in Kiel in November . " UB - 3 " was a little more than in length and displaced between , depending on whether surfaced or submerged . She carried two torpedo es for her two bow torpedo tube s and was also armed with a deck - mounted machine gun . She was launched and commissioned as SM " UB - 3 " in March 1915 . " UB - 3 " was broken into sections and shipped by rail to the Austro - Hungarian port of Pola in April for reassembly . She officially joined the Pola Flotilla on 1 May and departed on her first patrol for temporary duty in Turkey on 23 May , and was never seen again . A postwar German study concluded that " UB - 3 " was likely the victim of an unexplained technical problem in the absence of any minefields or enemy action . Design and construction . After the German Army ' s rapid advance along the North Sea coast in the earliest stages of World War I , the German Imperial Navy found itself without suitable submarines that could be operated in the narrow and shallow environment off Flanders . Project 34 , a design effort begun in mid - August 1914 , produced the Type UB I design : a small submarine that could be shipped by rail to a port of operations and quickly assembled . Constrained by railroad size limitations , the UB I design called for a boat about long and displacing about with two torpedo tube s . " UB - 3 " was part of the initial allotment of eight submarines — numbered to — ordered on 15 October from Germaniawerft of Kiel , just shy of two months after planning for the class began . " UB - 3 " was laid down by Germaniawerft on 3 November and was launched on 5 March 1915 . As built , " UB - 3 " was long , abeam , and had a draft of . She had a single Daimler 4 - cylinder diesel engine for surface travel , and a single Siemens - Schuckert electric motor for underwater travel , both attached to a single propeller shaft . Her top speeds were , surfaced , and , submerged . At more moderate speeds , she could sail up to on the surface before refueling , and up to submerged before recharging her batteries . Like all boats of the class , " UB - 3 " was rated to a diving depth of , and could completely submerge in 33 seconds . " UB - 3 " was armed with two torpedo es in two bow torpedo tube s . She was also outfitted for a single machine gun on deck . " UB - 3 " s complement consisted of one officer and thirteen enlisted men . Service career . The submarine was commissioned into the German Imperial Navy as SM " UB - 3 " on 14 March under the command of " Oberleutnant zur See " Siegfried Schmidt , a 27 - year - old , first - time U - boat skipper , and underwent trials in German home waters . As one of the UB I boats selected for Mediterranean duty , " UB - 3 " was readied for rail shipment . The process of shipping a UB I boat involved breaking the submarine down into what was essentially a knock down kit . Each boat was broken into approximately fifteen pieces and loaded on to eight railway flatcar s . " UB - 3 " was shipped to the port of Pola , site of ally Austria – Hungary ' s main naval base , on 15 April . After " UB - 3 " s parts arrived at Pola , it took about two weeks to assemble them . " UB - 3 " joined the Pola Flotilla ( ) on 1 May . By late May , " UB - 3 " had made her way down the Adriatic to the Austro – Hungarian port of Cattaro , the base from which most boats of the Pola Flotilla actually operated . For her first patrol , " UB - 3 " was loaded with ammunition for Turkish forces at İzmir , Turkey . Because of her limited range , " UB - 3 " was towed by an Austro - Hungarian Navy destroyer through the Straits of Otranto and cast off near the island of Kérkira . " UB - 3 " s planned route was south of the Ionian Islands , around the Peloponnese , through the Cyclades , north around Khios and Karaburun , and into the Gulf of İzmir . If all went well , " UB - 3 " would have arrived at İzmir on 28 or 29 May with about half her fuel left . The Germans received a garbled radio message from " UB - 3 " when she was about from İzmir , but were unable to completely understand it . No trace of " UB - 3 " has ever been found . " UB - 3 " was the first of the UB I boats to be lost during the war . A postwar German study concluded that " UB - 3 " s loss was probably the result of some unexplained technical problem , because there were no minefields along " UB - 3 " s route and no record of any attacks against U - boats in the area . British records , and some sources based on them , give the particulars of " UB - 3 " s demise as being in the North Sea on 24 April 1916 , which authors R . H . Gibson and Maurice Prendergast assert was actually the fate of . They also point out that " UB - 3 " had gone missing nearly a year before " UB - 3 " s supposed sinking in the North Sea .