German submarine U - 859 German submarine " U - 859 " was a German Type IXD2 U - boat built during World War II . She was one of a select number of U - boats to join the " Monsun Gruppe " or Monsoon Group , which operated in the Far East alongside the Imperial Japanese Navy . Construction . " U - 859 " was built in Bremen during 1942 and 1943 , and was heavily adapted following her completion in July 1943 , with the addition of a Snorkel to enable her to stay underwater for longer during the hazardous passage to Penang in Malaya . Thus she was not ready for war service until the spring of 1944 , when following her working up period and modifications she departed Kiel for the East . Service history . Although " U - 859 " only had a single war patrol from which she never returned , her six month career was highly eventful and carried her halfway across the world and into an entirely different theatre of conflict . Commanded by " Kapitänleutnant " Johann Jebsen , " U - 859 " sailed from Kiel for Penang on 4 April 1944 , carrying 31 tons of mercury in metal flasks destined for use in the Japanese munitions industry , and ( according to some sources ) uranium oxide also destined for Japan . She avoided shipping lanes and during her time in the North Atlantic , remained submerged for 23 hours every day , running on her schnorkel , surfacing for just one hour per day at 23 : 00 , later reduced to 15 minutes . Three weeks into her voyage , Jebsen saw a target he could not refuse . The MV " Colin " , formerly an Italian freighter taken over by American authorities and registered in Panama , was slowly steaming unescorted in the North Atlantic following engine failure . Three torpedoes sank her before the " U - 859 " went on her way southwards . The boat ' s voyage continued smoothly for the next two months , and she rounded the Cape of Good Hope and entered the Indian Ocean without further trouble . On 5 July she was spotted by a Lockheed Ventura aircraft , which swooped down on the boat only to be brought down by the anti aircraft guns . There were no survivors from the aircraft ' s crew . One rating of the U859 was killed and one officer seriously injured . ( Other sources say the attacking plane was a Catalina anti - submarine - plane ) . Her second victim was her most famous , and became one of the most famous treasure shipwrecks of the Twentieth Century . The unescorted Liberty ship was transporting a cargo of 3 million silver one - riyal coins from Aden to Ras Tanura in the Persian Gulf as part of an American government agreement with the Saudi royal family ; the silver coins had been minted in America for Saudi monarch King Abdul Aziz Al - Saud and were stacked in huge boxes in the hold , and went down with the ship when she was torpedoed at , about 100 miles south of the entrance to the Arabian Sea . A massive salvage operation in 1994 succeeded in retrieving many of the lost coins . Three days later another unescorted merchant , the British SS " Troilus " was also sunk , with six hands drowned . Loss . On 23 September " U - 859 " was running on the surface , within of Penang and the end of her voyage , when she was intercepted in the Malacca Straits by the British submarine , which had been forewarned of her arrival date and route by decrypted German signals . In difficult conditions with a heavy swell running and a second U - boat thought to be lurking , " Trenchant " s commander Arthur Hezlet carried out a snap attack using his stern torpedo tubes , hitting " U - 859 " amidships . The U - boat sank immediately in of water with several compartments flooded , and 47 men drowned , including her commander . Twenty of the crew did manage to escape however , opening the hatch in the relatively shallow sea and struggling to the calm surface . Eleven of the survivors were picked up by HMS " Trenchant " immediately following the sinking , and the remaining 9 were picked up by the Japanese after being adrift for 24 hours and were taken ashore to await repatriation . Salvage . In 1972 a total of 12 tons of mercury were recovered from the " U - 859 " and brought into Singapore . The West German Embassy claimed ownership of the mercury . The Receiver of Wreck took possession of the mercury , and the High Court of Singapore ruled that " the German state has never ceased to exist despite Germany ' s unconditional surrender in 1945 and whatever was the property of the German State , unless it was captured and taken away by one of the Allied Powers , still remains the property of the German State . . . "