The steel VIIC type submarine U-309 was launched from the Lubeck yard of Flender-Werke AG (Yard No 309) on 14th December 1942. She measured 67.10m x 6.2m x 4.74m and her tonnage was 871 submerged displacement tons, 769 surface displacement tons. She was powered by 2 x F46 four stroke six cylinder supercharged diesel engines by Germaniawerft producing 3200 metric horsepower driving twin shaftsand twin 1.23 metre propellers. She also had 2 x RP 137c double acting electric motors by Garbe, Laymeyer and Co delivering 740 shaft horse power for use while submerged. She was capable of diving to 230 metres. She had a maximum surface speed of 17 knots and submerged speed of 7 knots. During her eight previous sorties she had managed to sink only one vessel, SS Samneva while she was in convoy FTM47 in the English Channel.
Her loss, under the command of Oberleutnant Herbert Loder and with a crew of 46 men, was not confirmed until after the war but the Canadian Navy frigate St John was awarded a probable hit when she reported the action that took place in the Moray Firth on 16th February, 1945. Convoy WN.74 was steaming through the Moray Firth when St John reported as Asdic contact. The problem was that the reading had no Doppler effect and therefore was definitely stationary – they couldn’t decide if the contact was a U-boat or a wreck. However, an attack was ordered and, after three unsuccessful depth charge attacks, the fourth attack produced a mass of wreckage including charts, signal books and other miscellaneous items that clearly came from a U-boat.
A wreck was dived in 2001 in 58° 09.425’N, 002° 23.156’W and, although not positively confirmed as U-309, it is almost certain that the wreck of a Type VIIC U-boat lying with a 45 degree list to port and with damaged consistent with a heavy depth charge attack is indeed U-309. The bow of the wreck is missing and there is substantial damage to the pressure hull towards the stern. All this damage would indicate she was the victim of a successful depth charge attack. The seabed depth is 63 metres and the wreck has a least depth clearance of 60 metres.