SM UB - 7 SM " UB - 7 " was a German Type UB I submarine or U - boat in the German Imperial Navy ( ) during World War I . She disappeared in the Black Sea in September 1916 . " UB - 7 " was ordered in October 1914 and was laid down at the AG Weser shipyard in Bremen in November . " UB - 7 " was a little under 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 . " UB - 7 " was originally one of a pair of UB I boats sent to the Austro - Hungarian Navy to replace an Austrian pair to be sent to the Dardanelles , and was broken into sections and shipped by rail to Pola in March 1915 for reassembly . She was launched in April and commissioned as SM " UB - 7 " in the German Imperial Navy in May when the Austrians opted out of the agreement . Although briefly a part of the Pola Flotilla at commissioning , " UB - 7 " spent the majority of her career patrolling the Black Sea as part of the Constantinople Flotilla . The U - boat sank one ship of in September 1915 . In October , she helped repel a Russian bombardment of Bulgaria . She was considered for transfer to the Bulgarian Navy , but disappeared in late September 1916 before a transfer could take place . Her fate is officially unknown , but sources report that may have struck a mine or been sunk by a Russian airplane . 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 seas 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 - 7 " 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 - 7 " was laid down by Germaniawerft in Kiel on 30 November . As built , " UB - 7 " 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 - 7 " was rated to a diving depth of , and could completely submerge in 33 seconds . " UB - 7 " was armed with two torpedo es in two bow torpedo tube s . She was also outfitted for a single machine gun on deck . " UB - 7 " s standard complement consisted of one officer and thirteen enlisted men . While " UB - 7 " s construction neared completion in early March 1915 , Enver Pasha and other Turkish leaders were pleading with their German and Austro - Hungarian allies to send submarines to the Dardanelles to help attack the British and French fleet pounding Turkish positions . The Germans induced the Austro - Hungarian Navy ( ) to send two boats — its own Germaniawerft - built boats and — with the promise of " UB - 7 " and " UB - 8 " as replacements . When work on " UB - 7 " and " UB - 8 " was complete at the Germaniwerft yard , they were both 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 . The boats were ready for shipment to the main Austrian naval base at Pola on 15 March , despite the fact that the Austrian pair was still not ready . German engineers and technicians that accompanied the German boats to Pola worked under the supervision of " Kapitänleutnant " Hans Adam , head of the newly created U - boat special command ( ) . Typically , the UB I assembly process took about two to three weeks , and , accordingly , " UB - 7 " was launched at Pola sometime in April . Career . During her trials , " UB - 7 " developed a leak which took some time to repair . In the meantime , she was assigned the Austrian number of " U - 7 " and an Austrian commander . Her German crew at Pola — since it was still the intent for " UB - 7 " to be transferred to the " K . u . K . Kriegsmarine " — wore either civilian clothes or Austrian uniforms . As time dragged on , the Austrian " U - 3 " and " U - 4 " were still not ready , and eventually Admiral Anton Haus , the head of the Austrian Navy , reneged on his commitment because of the overt hostility from neighbor and former ally Italy . With the change of heart from the Austrians , Germany resolved to retain " UB - 7 " and send her to the aid of the Turks . So , upon completion of her leak repairs , the boat was commissioned into the German Imperial Navy as SM " UB - 7 " on 6 May under the command of " Oberleutnant zur See " Wilhelm Werner , a 26 - year - old native of Apola . At commissioning , the boat temporarily joined the Pola Flotilla ( ) . Because of her limited range , " UB - 7 " would not have been able to make the entire journey to Turkey , so on the night on 15 / 16 May , she was towed by the Austrian destroyer through the Straits of Otranto and into the Ionian Sea . By June , " UB - 7 " had reached Smyrna — not having any success on her journey there — and joined and " UB - 8 " in the Constantinople Flotilla ( ) . Once there , " UB - 7 " was ineffective because she was hampered by her limited torpedo supply and her weak engines , which made negotiating the strong Dardanelles currents nearly impossible . Because of this , " UB - 7 " was sent to patrol in the Black Sea in July , cruising without success from the 5th to the 22nd . In September 1915 , " UB - 7 " and " UB - 8 " were sent to Varna , Bulgaria , and from there , to patrol off the Russian Black Sea coast . On 18 September , " UB - 7 " torpedoed and sank the British steamer " Patagonia " about from Odessa . The cargo ship , of , was the only ship credited to " UB - 7 " , and the only one sunk by any of the Constantinople Flotilla in the month . Because Bulgaria had joined the Central Powers , battleships of the Russian Black Sea Fleet , and aircraft from the seaplane carrier s and began attacks on Varna and the Bulgarian coast on 25 October . " UB - 7 " and " UB - 8 " , both based out of Varna by this time , sortied to disrupt the bombardment . Off Varna on the 27th , " UB - 7 " got in position to fire a torpedo at the ( most well - known under her former name of " Potemkin " ) . Although " UB - 7 " s crew heard what they thought was the torpedo explode , it did not hit " Panteleimon " . Despite the lack of success , the attempt did cause the Russians to break off their attacks and withdraw . In early 1916 , " UB - 7 " and " UB - 8 " were still cruising in the Black Sea out of Varna . The Germans did not have good luck in the Black Sea , which was not a priority for them . The Bulgarians , who saw the value of the submarines in repelling Russian attacks , began negotiations to purchase " UB - 7 " and " UB - 8 " . Bulgarian sailors practiced in the pair of boats and technicians were sent to Kiel for training at the German submarine school there . The transfer of " UB - 8 " to the Bulgarian Navy took place on 25 May 1916 , but for reasons unreported in sources , " UB - 7 " remained under the German flag . In July 1916 , the Germans sent to mine off Novorossisk . To attempt to neutralize any Russian response , " UB - 7 " — under the command of Hans Lütjohann , who had taken over for Werner when he returned to Germany to command the new — was stationed off Sevastopol to attack any ships that sailed in response to the mission . Unfortunately , Russian seaplanes spotted " UB - 7 " and bombed the U - boat , preventing her from accomplishing her goal . With the submarine out of the way , Rear Admiral Aleksandr Kolchak sortied with dreadnought , cruiser , and five destroyers . The Russian fleet engaged " Breslau " , which was forced to abort her mission and retire . Sources are quiet on damage , if any , suffered by " UB - 7 " . Fate . On 27 September 1916 , " UB - 7 " departed Varna for operations off Sevastopol and was never heard from again . According to some sources , " UB - 7 " was mined somewhere in the Black Sea . In June 1917 , a Russian pilot captured by the Germans reported that a Russian airplane bombed and sank " UB - 7 " on 1 October at position , near the Chersones Lighthouse . Authors Dwight Messimer and Robert Grant are each dubious of this claim , and the fate of " UB - 7 " is still officially unknown . Among the fifteen men lost on " UB - 7 " were the Constantinople Flotilla ' s senior radio officer , and the first Bulgarian submariner lost during the war , a trainee from Vidin .