UB-81 was ordered by the GIN on 23 September 1916 and her keel was laid down on 5 January 1917.[2] She was built by AG Weser of Bremen and following just under a year of construction, launched at Bremen on 4 August 1917. UB-81 was commissioned later that same year under the command of Reinhold Saltzwedel. Like all Type UB III submarines, UB-81 carried 10 torpedoes and was armed with a 8.8 cm (3.46 in) deck gun. UB-81 would carry a crew of up to 3 officer and 31 men and had a cruising range of 8,180 nautical miles (15,150 km; 9,410 mi). UB-81 had a displacement of 516 t (508 long tons) while surfaced and 647 t (637 long tons) when submerged. Her engines enabled her to travel at 13.4 knots (24.8 km/h; 15.4 mph) when surfaced and 7.5 knots (13.9 km/h; 8.6 mph) when submerged.
On the night of 30 November/1 December 1917 she torpedoed and sank the 3,218 ton British steamer Molesey 12 miles west-south-west of the Brighton Light Vessel.[6]
^ abHelgason, Guðmundur. "WWI U-boats: UB 81". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net. Retrieved 29 September 2010.
^ abHelgason, Guðmundur. "Ships hit by UB 81". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net. Retrieved 29 September 2010.
^Helgason, Guðmundur. "Ships hit during WWI: Molesey". German and Austrian U-boats of World War I - Kaiserliche Marine - Uboat.net. Retrieved 29 September 2010.