21 August 1918, the UC II class coastal mine laying submarine, UC-70 departs Zeebrugge under the command of Oberleutnant sur zee Karl Dobberstein, to embark on a war patrol off the east coast of England. The UC-70 was one of many submarines operating in the North Sea causing significant loss to British and Allied shipping. The aim of this inter-club dive was to return to the sub under licence, and record its current condition, obtain photographs and video and submit to Historic England for their records.
Built by Blohm & Voss (Hamburg) and commissioned 20 November 1916, The UC-70 measured over 50.35m in length, a beam of 5.22m and a draught of 3.64m. She had 2 bronze screws (propellers) powered by 2 x 6 cylinder diesel engines and 2 x 460kW electrical motors. At the surface, she had a maximum speed of 12 knots and when submerged, her speed was no greater than 7.4 knots. The UC-70 had a range of 10,420 nautical miles whilst surfaced and 52 nautical miles submerged. Her maximum operating depth was 50m.
[left: UC-55 Type II Coastal Mine Laying Submarine in Construction at……..]
The UC-70 had a complement of 26 and the submarine was armed with 6 x 1m mine tubes, each able to carry 3 mines per tube. A total of 18 UC 200 type mines. 2 external torpedo tubes to the bow and 1 stern torpedo tube were able to launch a total of 7 torpedoes, and on the deck of the boat, an 88mm UK L/30 deck gun completed her arsenal.
[Above: Silhouette of a Type II Mine Laying Submarine]
Since her commission, the UC-70 embarked on 10 successful patrols and was credited with over 54,000tons of damage / sinking to British and Allied merchant shipping. 33 ships in total were sunk by UC-70 by either torpedo or mine. Her last victim was the SS Giralda, a 1,100ton iron steamship which lay in 13m, approx. ½ mile North of Kettleness Point (South of Runswick Bay). SS Giralda was torpedoed by UC-70 on the 28 August 1918.
On the 28 August 1918, a Blackburn Kangaroo patrol aircraft spotted a trail of oil off Whitby. It was traced back to reveal an object submerged below the surface, believed to be a possible U-Boat. HMS Ouse, a River-Class Destroyer was soon to the scene and after witnessing the Blackburn’s bombing, HMS Ouse supported the attack with a salvo of between 7 to 10 depth charges being launched resulting in further oil and debris being observed on the surface.
Now, over 100 years have passed and the UC-70 is a protected wreck and can only be dived under licence. She rests in approx. 25m of seawater on a seabed of mud, sand, gravel and shell. With a licence obtained from Historic England by Dave English (Doncaster Sub Aqua Club) 18 divers, 5 clubs (Doncaster, Humber, Selby, Grimsby & Rotherham), 3 boats (Valiant, Nemo & Manta) planned and successfully dive the UC-70 to view and record its current condition.
[Left: Divers prepare the boat in readiness for the journey to the UC-70]
Leaving the harbour we planned to dive the UC-70, 2 hours after low water. The weather and sea state were perfect, and shotting a cigar tube nearly 30m below was completed by the Valiant crew with precision. With no tide running, the first wave of divers entered the water uncertain of what to expect.
Shot LineThe shot was up tide of the bow by approx. 5m. A shadow loom in the distance, and Allan and I gently approached. It was a matter of seconds before wreckage of the UC-70 emerged below and the shape of the bow appeared directly in front.
Depth – 24m
[Above – Sketch by John Liddiard published in Diver Magazine]
As we approached the forward part of the deck, we clearly had 5-7m of visibility with particles in the water providing the appearance of a snowy back drop. As we rose gently to the deck of the boat, what appears to be an anchor winch stands proud. The 2 bow torpedo tubes were not present on the sub or the seabed suggesting that these had been removed by previous salvage operations. Shortly after the anchor winch, 6No 1m wide mine tubes, empty of its payload descend in to the dark and desolate belly of the boat. Each tube had the capability of stowing and releasing 3 mines each. A total of 18 UC 200 mines which were likely to have been released on the U-boats patrol before its sinking.
After the mine tube, [Picture Left] an open hatch came into view. It is hard to imagine the fear of the 31 German submariners, scrambling through a 50m x 5m vessel, full of machinery to escape the water rushing through multiple penetrations, flooding each compartment with sea water, starving the vessel of air. A gentle pause in the dive to remember those who lost their lives as the submarine rests motionless on the seabed.
Continuing towards the stern, the 88mm UK L/30 deck gun [Picture right] stands in solitude, locked in its travelling position but ready to explode into action when the need arises. The gun facing forward is now covered with marine life, with the barrel of the gun now forming a natural habitat to support marine life.
[Left: Small fish inhabits that 88mm deck gun]
Aft of the gun is a mast that houses the search periscope. The tapered structure rises a couple of meters above the deck looming towards the surface. Retracted to avoid detection, the periscope remains intact and covered in marine life.
Resting on the port side of the submarine, are the scattered plates of what once was the conning tower of the submarine. Once used for navigation and controlling attacks on enemy vessels, it now lay broken between ship and the seabed unrecognisable. In what appears to be a hatch, a hollow tube protrudes from within possibly the attack periscope. A smaller periscope used to allow the submarine to remain undetected whilst submerged. During this dive, it was difficult to identify certain parts of the wreck due to the devastation.
As we continue to swim along the port side, the outer and inner hull deteriorated, revealing an array of twisted metal and machinery providing a new habitat for shoals of mackerel and other marine life. The port side hydroplane has detached itself and rests between the hull and seabed and above, the internal structure becomes more apparent with the erosion of the hull structure. Between the hulls, the port side a pressurised cylinder to blow the ballast tanks remains intact and can be seen in full
At the stern, nothing is recognisable. The wrath of war, nature and historic salvage has all played their part in the destruction of this vessel. Pipes, valves and other machinery lay exposed revealing the complex engineering and the management of space internally. With no sight of the bronze screws, or other prominent features expected at the stern, we headed back to the shot and asked further questions of ourselves to the sinking of the ship and what did UC-70 leave behind after the successful depth charging from HMS Ouse.
As we surfaced after a 35minute run time, we embraced happy divers all around who obviously enjoyed the dive as much as we did. The conditions and the professionalism of the crew made the dive the success it was and look forward to returning to the site in the near future, to investigate those questions that arose during the dive, and with an objective to gather more evidence and information on the UC-70.