Building ordered on 25 November 1910, laid down at the Kaiserliche Werft Danzig with yard number 16 on 14 November 1911, launched on 6 March 1913, launched on 25 November 1913, handed over to England on 1 December 1918 and broken up at Blyth between 1919-1920. Sunk during the First World War 44 merchant ships with a total gross tonnage of 46.365 tons and the British 7.940 tons auxiliary cruiser HMS India.
Double hulled project type 20 submarine wit as sister ships U 20, U 21 and U-22 which were the first German submarines fitted out with diesel engines. Displacement 650 (surfaced)-873 (submerged) tons and as dimensions 64,15 x 6,10 x 3,58 metres or 210.6 x 20.0 x 11.9 feet. Maximum diving depth 50 metres. Machinery consisted of 2-6 cylinder 850 hp MAN diesel engines and 2-600 hp AEG double Motordynamos allowing a speed of 15,4 (surfaced)-9,3 (submerged) knots. Crew numbered 35 men included 4 officers. Original armament 4-50cm torpedo tubes (bow 2, stern 2) or which she carried 9 torpedoes and 1-8,8cm gun (later 2?).
