U 77

U 73 (of the same type as U 77) in dry dock

On, or just after 7 July 1916 95 in 100 metres

Built: 1915 by AG Vulcan, Hamburg

Construction: steel 755 grt (displacement, surfaced), type UE 1 u-boat, length 56.8 m, beam 5.9 m, draught 4.86 m (height 8.25m)

Propulsion: twin screw, 2 x 6-cyl diesels 900 HP each, 2 x electric motors 900 HP each

Armaments: 2 x 50cm external torpedo tubes (bow and stern) , 4 torpedoes, 1 x 8.8cm SK L/30 deck gun, 38 mines

The U 77 was a type UE 1 ocean mine laying boat from WWI, 10 boats of this type were commissioned and they were extremely successful raiders. The UE 1 boat, U 73, was responsible for the sinking of the 48,000 grt SS Britannic in November 1916 and the U 75 laid the mines that sank HMS Hampshire in June 1916 , claiming the life of Lord Kitchener. The U 77 was not so successful.

She was ordered on 9 March, 1915, launched 9 January, 1916 and commissioned 10 March. During May and June she was at Kiel school and first entered the North Sea together with U 76 on 29 June when she joined the 1st Half Flotilla.

On 1st July, she was given orders for her first patrol, which was to proceed to the Moray coast to lay mines between Kinnaird Head (Fraserburgh) and Knock Head (Whitehills, just west of Banff), an area where it was believed naval vessels would pass, on their way to the deep water base at Invergordon.

We were able to obtain a translation of her orders for the patrol:

She left Heligoland on 5th July under the command of Kaptlt Erich Gunzel with a crew of 33 and a load of 34 Type II E-mines onboard. She did not return from her mission and there was no trace of her crew, all are presumed lost. We know that she managed to reach her area of operations and laid some of her mines, they were found and destroyed by the navy on 26 July (this was reported in the Bi-monthly Minesweeping Report). None of her mines caused any damage to shipping. There were no British naval reports of engagement with any U-boats at that time so it was assumed that she had been lost in an accident while laying her mines, or on her voyage home.

The last sighting of her was at 4pm on 7 July, 1916 when a U-boat, presumed to be U 77, was spotted heading north, slowly about 50miles east of Kinnaird Head. For a period in the late nineties, she was thought to have been found off Dunbar, south of Edinburgh, but that wreck has, since 2005, been generally accepted to be that of the U 74. So, her whereabouts and actual cause of sinking have been a mystery for nearly 105 years.

Our team were aware of her existence but we had no reliable position for the wreck and, given she could have been lost on her return from patrol, it wasn't even clear that she was in the Buchan area. We did have one mark, which a side scan survey had indicated as a possible submarine, about 20 miles ESE of Kinnaird head but when we dived the wreck, we identified it as the Subworker, a steam dredger which foundered in 1913. We had pretty much given up hope of ever finding the her remains when, one rainy winter's day in early 2020, our old friend and expert wreck researcher, Kevin Heath, got in touch to inform us that he and Michael Lowrey had reviewed the available information on the U 77 and felt he had a reliable suggestion for her position.

Kevin and Michael had pieced together some key information that we had missed;

Her orders were to lay mines in a very specific area, bounded east by Kinnaird Head and west by Knock Head, and by 2 miles north and 4 miles north of the connecting line between the two points.
She would have laid her mines in depths of 100m or less. There are many deep trenches in this area so her mine laying positions would have been limited to the shallower sections.
Kevin and Michael were able to obtain locations for the mines which had been discovered in the area after the 7th July. There were only 9 mines found, so 25 were unaccounted for. It was clear that she had not finished her mission and would likely be still in the area, furthermore with so many mines unaccounted for, it added weight to the theory that she had been lost to one of her own mines in an accident, possibly while laying the 10th mine.
A UK Hydrographic Office report noted a wreck in the area giving off oil. It was more accurately side scanned in 1987, and a wreck 47m long and 6.4m high was seen with a prominent "funnel" amidships. Kevin suspected that the "funnel", typically one of the first components of a wreck to collapse and therefore surprising to be still in place, could, in fact, be a conning tower. Furthermore, the dimensions of the wreck tie in very closely with those of the pressure hull and height of a type UE 1 u-boat.

The wreck noted in the Hydrographic Office report was adjacent to the lines of 9 mines that the U 77 had successfully laid and within the 100m depth of her limit of mine laying operations. There are no other reliable marks in the area. So if she had been sunk by her own mine, this mark is her most likely position.

Super wreck detective work!

In fact, this wasn't a new wreck position for us. We had been aware of it for many years but it looked quite small, we assumed it to be a steam trawler and, given its depth and its distance from Peterhead (2 hours steaming) we had prioritised other, more interesting and less challenging marks for investigation. We had failed to appreciate the significance of the midships "funnel" comment on the survey report and we were not aware of the specific details of the U 77 area of operation.

However, armed with this new research, and the thought that we might be able to solve the 105 year old mystery of the U 77, we prioritised the mark for investigation and possible diving in 2020/21. It would be a serious undertaking though, our deepest wreck to date. Careful planning would be required together with work up preparations, surface support and the right weather and sea conditions.

The 2020 season did not allow such grand adventures, but in 2021 we targeted the wreck for exploration from the surface - despite our faith in Kevin and Michael's research, we did not want to risk a dangerous dive to 100m to find an old trawler. We made two attempts to find and film the wreck from the surface using a borrowed ROV operated from the RIB - both attempts failed with no video to show, and the near loss of a £7,000 ROV.

However, we had better luck with a borrowed dropcam (an underwater camera and light on the end of a long cable, hooked into a surface video display). Naomi and Jim headed out on 2nd September in flat calm seas to make a third attempt to film the wreck. It was not easy but we were able to get some footage which confirmed the wreck to be of a submarine - and it can only be the U 77.

She lies on a mud seabed in 100m running approximately east/west, in poor visibility (unexpected for a Moray coast wreck) and wrapped in nets and ropes. From the sounder trace, we can see that the westward end of the wreck is intact but the eastward end is broken up and there is a debris field here. We are not yet certain which end is which, but bow to the west and stern to the east would be consistent with the theory of her loss was caused by one of her own mines exploding in, or near, her stern minelaying chute (this is also how U 74 met her fate). The stills from the video show the pressure hull and outer hull, with penetrations for possibly the depth gauge equipment, the hull is curved to the seabed and there looks to be torpedos or pressure vessels lying around her on the seabed.

Special thanks to Michael Lowrey and Kevin Heath for their help in finding this wreck and also to Ian Macdonald, owner of Buccaneer Ltd. for kindly lending us the ROV and dropcam equipment.

U 77 Update (August 2024)

We visited the site of what we believed to be the U 77 on the diving support vessel MV Clasina with her crew and skipper, Bob Anderson. Onboard were a group of divers experienced at greater than 100m dives who were in the area primarily to search for and dive HMS Hawke as part of the Lost In Waters Deep project, however due to weather, they were unable to visit the HMS Hawke site so agreed to help with the U 77 identification. Also onboard was Kevin Heath who had helped us with the research that led to the location of the U 77. Kevin had brought his C-Max CM2 sidescan sonar so we could get some good images of the wreck.

On 13th August, six divers descended to the wreck in 100m. The shot line was off the wreck by some 10m, it was difficult to shot given her small width, but reeling out lines, they eventually found her hull.

Divers reported that the shot was on the wreck’s port side near the stern. They reported seeing hydroplanes, external torpedo tubes and one diver reported an intact large tube on the port side with what looked like a hatch inside, about 2m from the opening. This would have been one of the mine laying chutes. They followed the deck, noting what looked like pressure vessels on top of the pressure hull. They passed a raised cylindrical deck hatch (which matches the mine loading hatch). They noted some damage to the hull affecting the rear of her saddle tank (buoyancy lank) to starboard. Back on the deck, they saw a small gun, still in its mounts and pointing to the surface. At this depth, the divers were accumulating a larger decompression penalty for every minute spent. Already this was approaching well over two hours, so they decided to make their way back to the shot line and to the surface. The last diver reached the surface 3 hours and 10 minutes after leaving it.

The dive details confirmed beyond doubt that this is the resting place of the U 77 and her crew of 33. We have reported her position and state to the German Wargraves Commission, they have initiated the process to have her wreck formally identified as a War Grave.

However, we had expected to see significant damage to the stern area based on our assumption that one of her mines had detonated there or in the delivery chute while being deployed. This assumption had been further supported by our sonar scans when we first visited the site. The divers reported that her stern, and specifically her mine chute, is intact. Other than some noted damage to her starboard saddle tank, the wreck is in excellent condition for her age. So what could have sunk her?

The answer was only available once we saw the results of the side scans. We deployed Kevin’s sidescan towed fish on 300m of line off the stern of the Clasina and Bob, deftly manoeuvred the Clasina so that we could make several close passes of the wreck to the north and south. The towed sonar was between 25 and 30m off the sea bed. Kevin managed the technology and we managed to gain some excellent images of her port and starboard sides. Charlie Comrie our onboard photographer was able to use Photoshop to join the port and starboard images and overlay the U 77’s deck plans so that we could get a better impression of her state.

We could see that her overall shape matches exactly to the design drawings. Key features of the conning tower, gun, mine hatch and stern hydroplanes are visible. However there is significant bevelling of her hull to the starboard side, just aft of the saddle tank and this damage continues on to her port side where some items of wreckage still appear on the seabed.

This damage would be consistent with her colliding with one of her own mines shortly after deployment. We suspect this could have either been caused by one of her mines ascending below her and detonating or a navigation error resulting in her colliding with a previously laid mine. Regardless, the damage to her pressure hull and buoyancy tanks would have resulted in her rapid and uncontrolled descent to the seabed.

We’d like to thank Kevin Heath (research and sidescan), Bob Anderson and crew of the MV Clasina and the Gasperados dive team of: Steve Mortimer, Will Schwarz, Paul Downs, Simon Kay, Clare Fitzsimmons, Jakob MacKenzie and Rick Waring plus dive support team of Barbara Mortimer, Dan O’Callaghan, Steve Green, Paul Southby without whom we would not have been able to confirm the identity of the wreck and complete the story of the U 77.

Composite sidescan image, made of a port and starboard run joined together c/o Charlie Comrie. Bow to left. Note the damage to her saddle tank on her starboard quarter. This was probably caused by one of her own mines and led to her loss.