A German Type UC II submarine, UC-55 had a displacement of when at the surface and while submerged. She had a length overall of, a beam of, and a draught of. The submarine was powered by two six-cylinder four-stroke diesel engines each producing , two electric motors producing, and two propeller shafts. She had a dive time of 48 seconds and was capable of operating at a depth of. The submarine had a maximum surface speed of and a submerged speed of. When submerged, she could operate for at ; when surfaced, she could travel at. UC-55 was fitted with six mine tubes, eighteen UC 200 mines, three torpedo tubes, seven torpedoes, and one Uk L/30 deck gun. Her complement was twenty-six crew members.
Service
In 6 patrols UC-55 was credited with sinking 9 ships, either by torpedo or by mines laid.
Loss
UC-55 sailed from Heligoland on 25 September 1917 to lay mines in the Lerwick Channel, the southern approach to the port of Lerwick in the Shetland Islands. On 29 September, just as she started dropping her mines, she suffered a loss of trim which resulted in her diving beyond her rated maximum dive depth. This in turn resulted in the forward compartment flooding, the batteries failing, and chlorine gas developing. She was forced to surface to ventilate the boat, but when she surfaced, the rudder refused to answer the helm due to the lack of battery power. Her captain then gave orders to destroy secret documents and codebooks and set scuttling charges in the mine room and engine room. While the charges were being placed she was sighted by the armed trawlerMoravia and the destroyers and. A 12-pdr shell from the Sylvia hit the submarine's conning tower, killing her commander, Horst Ruhle von Lilienstern, and a second shell hit the hull and she began to sink, after which two depth charges were dropped right beside the UC-55, resulting in the U-boat blowing up. The Moravia then closed with the wreck, fired two more shots into her, and dropped a final depth charge. Of the submarine's crew, 17 were taken prisoner, and 10 were killed.
Location of Wreck
The wreck of UC-55 is thought to lie in at. This site was surveyed on 3 July 1985, when side scan sonar discovered the wreck of a submarine lying on its keel, and measuring approximately high and long.
