SM UB-116
SM UB-116 is the wreck of a German Imperial Navy submarine that lies on the seabed in the waters of the Pentland Firth, off the northern coast of Scotland near Hoxa Head at the southern entrance to Scapa Flow in Orkney. It is one of the most historically significant submarine wrecks in British waters, representing both a dramatic episode from the final days of the First World War and a rare example of an intact U-boat resting in relatively accessible depths. For divers and historians alike, the site carries enormous weight, sitting within one of the most storied stretches of water in naval history.
UB-116 was a Type UB III minelaying and torpedo submarine commissioned into the German Navy in 1918. Its fate was sealed on the night of 28 October 1918, just two weeks before the Armistice that ended the First World War, when it attempted a daring solo mission to penetrate Scapa Flow — the great British naval anchorage in Orkney where the bulk of the Grand Fleet was stationed. The mission was audacious to the point of recklessness: the plan was for UB-116 to slip through Hoxa Sound under cover of darkness, infiltrate the heavily defended anchorage, and attack the British fleet. The Royal Navy, however, had laid a sophisticated hydrophone detection network and controlled minefields across the approaches to Scapa Flow. As UB-116 crept through Hoxa Sound, shore operators detected its passage on their hydrophones and detonated the minefields remotely. The submarine was destroyed instantly, and all 36 men aboard were killed.
The wreck lies in approximately 58 metres of water, resting largely intact on the seabed, which speaks to the nature of the destruction — the detonating mines cracked the hull catastrophically rather than scattering it entirely. The submarine sits more or less upright, recognisable in its form even after more than a century on the bottom. Marine growth has colonised the steel extensively, and the cold, dark waters of the Pentland Firth have preserved the general outline remarkably well. Divers who have visited the site describe the eerie sensation of encountering the conning tower rising from the silty bottom, festooned with anemones and inhabited by large wrasse and cod. The visibility in these waters is variable but can be excellent on the right tidal conditions.
The surrounding waters of Hoxa Sound and the wider Scapa Flow basin are extraordinary in terms of naval heritage density. Scapa Flow itself is world-famous as the site where the interned German High Seas Fleet was scuttled in June 1919, and several of those wrecks — including battleships and cruisers — lie within diving distance. The landscape above water is quintessentially Orcadian: low, rolling hills, wide skies, dramatic light, and the constant presence of the sea. The headlands of South Ronaldsay and Flotta frame the sound, and the view across to the islands on a clear day has a stark, elemental beauty.
As a war grave, UB-116 is protected under the Protection of Military Remains Act 1986, which means that diving on the wreck is controlled and that no artefacts may be removed. Divers wishing to visit the site must obtain the appropriate licences, and the depth — around 58 metres — puts it in the technical diving category, requiring advanced training and equipment, typically involving mixed gas or trimix. The site is reached most practically by live-aboard or day-charter dive boats operating out of Stromness or St Margaret's Hope in Orkney. The calmer summer months between May and September offer the best sea conditions, though tidal planning is essential given the fierce currents that run through the Pentland Firth.
One of the more haunting aspects of the UB-116 story is the question of what drove the crew to attempt such a mission so close to the end of the war. Morale in the German Navy was collapsing; mutiny had broken out in Kiel and Wilhelmshaven within days of UB-116's departure. Whether the crew knew how close the Armistice was, and whether the mission was intended as a final act of desperate gallantry or represented an order they had no choice but to follow, remains a matter of historical reflection. The 36 men who perished remain entombed within the wreck to this day, making every dive on the site an act of solemn commemoration as much as exploration.