Protected wreck

UC-70 was a Type UC II coastal mine-laying submarine, commissioned into the German Imperial Navy in November 1916. She carried up to eighteen mines in six sloping tubes, seven torpedoes and an 88-millimetre deck gun. Two engines and greater range improved on the smaller first type and allowed mine attacks around the British coast. In ten patrols UC-70 sank or damaged forty ships totalling about 54,591 tons. On 21 August 1918, twenty-nine-year-old commander Karl Dobberstein left Zeebrugge to lay mines on the convoy route between Holland and England and then attack shipping off England's east coast. What she did during the following week is not fully known.

On 28 August a Blackburn Kangaroo aircraft of 246 Squadron, flown by Lieutenant Arthur Wearing, saw a long oil trail off Whitby. He followed it to the shadow of a submarine below the surface and dropped a bomb. HMS Ouse arrived, saw the explosion and spreading oil, and dropped between seven and ten depth charges. More oil, air and wreck pieces rose. UC-70 may already have struck a British mine and been lying on the bottom making repairs, which would explain the leak, but that remains a strong possibility rather than a proved first cause. The aircraft found and damaged her; the combined bombing and depth charges ended the submarine.

All thirty-one officers and men died, including Karl Dobberstein. When British naval divers entered the wreck in September and October 1918, they found the hatches open, suggesting that at least some men attempted to escape after the attack. No one reached safety. The divers recovered three bodies, including the commander, while searching for codes and other intelligence. Human bone remains visible at the damaged stern today and may belong to a torpedo worker, engine-room man or stoker, but it has not been named. The wreck must therefore be understood as the resting place of crew members, not simply as a diving attraction or store of reusable metal.

UC-70 lies upright with a slight lean to port in roughly 21 to 28 metres of water off Whitby. Much outer plating has corroded or fallen away, exposing the ribs of the fuel and ballast tanks, but the stronger inner pressure hull remains largely intact. The deck gun, six mine-tube openings, two periscopes and bow diving planes survive; the bow is badly damaged by the attack. The conning-tower plating has fallen to port. Later salvors appear to have used explosives at the stern to remove valuable metal, including the stern torpedo tube. A Chinese porcelain plate recovered from the galley is an unexpected personal or service object, but its route aboard is unknown. The wreck was protected in 2017.

UC-70 represents the most successful class of mine-laying submarine when success is measured by ships sunk. Small minefields laid secretly on trade routes let one boat harm shipping long after it had left, and UC-70's forty victims show that reach. Her loss also joined a new long-range British patrol aircraft with a destroyer: the oil trail made a hidden submarine visible, the aircraft marked and bombed it, and Ouse completed the attack. For Whitby the wreck is part of the coast's First World War story and a long-standing local dive site. Local knowledge helped later survey work, but removed metal and exposed human remains show why protection and respect are essential.