A German Type UB II submarine, ‘’UB-18’’ had a displacement of when at the surface and while submerged. They had a length overall of , a beam of , and a draught of . The submarine was powered by two Daimler six-cylinder four-stroke diesel engines each producing (a total of ), two Siemens-Schuckert electric motors producing , and one propeller shaft. She had a dive time of 45 seconds and was capable of operating at a depth of .
