She was commissioned into the German Imperial Navy on 22 January 1918 as SM UB-118.

[Note 1] UB-118 was surrendered to the Allies at Harwich on 21 November 1918 in accordance with the requirements of the Armistice with Germany.

She was allocated to British explosive trials at Falmouth (see UB-86, UB-97, UC-92, UB-106, UB-112 and UB-128), but began to take water while in tow from Devonport to Falmouth, and was therefore sunk by her escort on 21 November 1920.

Like all Type UB III submarines, UB-118 carried 10 torpedoes and was armed with a 8.8 cm (3.46 in) deck gun.

UB-118 would carry a crew of up to 3 officers and 31 men and had a cruising range of 7,280 nautical miles (13,480 km; 8,380 mi).