SM U-104^{[Note 1]} was a German Type U 57 U-boat during the First World War. U-104 was built at AG Weser in Bremen, launched on 3 July 1917 and commissioned on 12 August 1917. She completed four patrols under Kptlt. Kurt Bernis and was responsible for the sinking of nine vessels of a total of 14,721 gross register tons (GRT).^[3]

On 25 April 1918 the U-104 was engaged by USS Cushing in St. George's Channel and severely damaged. Later the same day HMS Jessamine came upon her and dropped further depth-charges, sinking her and leaving but a single survivor of her 42-member crew. The wreckage lies at position 51°59′N 6°26′W / 51.983°N 6.433°W / 51.983; -6.433.

Date	Name	Nationality	Tonnage[Note 2]	Fate[4]
26 October 1917	Sapele	United Kingdom	4,366	Sunk
15 December 1917	Maidag	Norway	1,253	Sunk
21 December 1917	Spro	Norway	1,507	Sunk
25 December 1917	Ajax	Denmark	1,018	Sunk
2 March 1918	Kenmare	United Kingdom	1,330	Sunk
12 April 1918	Njaal	Russian Empire	578	Sunk
16 April 1918	Widwud	Russian Empire	299	Sunk
20 April 1918	Lowther Range	United Kingdom	3,926	Sunk
22 April 1918	Fern	United Kingdom	444	Sunk

• U-boat Campaign (World War I)

• Gröner, Erich; Jung, Dieter; Maass, Martin (1991). U-boats and Mine Warfare Vessels. German Warships 1815–1945. Vol. 2. Translated by Thomas, Keith; Magowan, Rachel. London: Conway Maritime Press. ISBN 0-85177-593-4.