HMS Undine was a British U class submarine

British U class submarine

The British U class submarines were a class of 49 small submarines built just before and during the Second World War...

 built by Vickers Armstrong

Vickers Armstrong

Vickers-Armstrongs Limited was a British engineering conglomerate formed by the merger of the assets of Vickers Limited and Sir W G Armstrong Whitworth & Company in 1927...

, Barrow-in-Furness

Barrow-in-Furness

Barrow-in-Furness is an industrial town and seaport which forms about half the territory of the wider Borough of Barrow-in-Furness in the county of Cumbria, England. It lies north of Liverpool, northwest of Manchester and southwest from the county town of Carlisle...

. She was laid down on 19 February 1937 and was commissioned on 21 August 1938. She was the lead ship of the first group of the U class, which is sometimes called the Undine class.

Sinking

Undine was on her fourth war patrol in January 1940 when her sonar

Sonar

Sonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels...

failed due to a leak. At 0940 on 7 January, she sighted what was thought to be three trawlers 20 miles west of Heligoland; but were in fact the German auxiliary minesweepers M-1201, M-1204 and M-1207. She unsuccessfully attacked the leading vessel, but the minesweepers counter attacked and forced her to dive. Undine was at 50 feet and proceeding blind due to the loss of sonar. After five minutes with no further attacks, she raised her periscope. As she did so, an explosion shook the submarine, blowing her upwards and rendering the hydroplanes useless. Without the use of the hydroplanes, escape would have been impossible and the order to abandon ship was given. Whilst the crew entered the water, to be picked up by the minesweepers, Undine was scuttled.