SM U-31[Note 1] was one of the 329 submarines serving in the Imperial German Navy in World War I. U-31 was engaged in the naval warfare and took part in the First Battle of the Atlantic.

[2] U-31 was fitted with two Germania 6-cylinder two-stroke diesel engines with a total of 1,850 metric horsepower (1,361 kW; 1,825 bhp) for use on the surface and two Siemens-Schuckert double-acting electric motors with a total of 1,200 PS (883 kW; 1,184 shp) for underwater use.

[2] The wreck of U-31 had been discovered in 2012 about 55 miles (89 km) off the coast of East Anglia during surveys made in preparation for the construction of an offshore wind farm.

However, the wreck was not formally identified until 9 September 2015 when the Dutch Lamlash wreck-diving team discovered the hull number engraved on a salvaged item of navigation equipment.

This wreck could be classified as a World War I SM U-31 series U-boat 2015: Wreck positively identified by Dutch divers from mv Lamlash - Haarlem as the SM U-31 (Hull number found on a “Fahrt Tabelle” (Manoeuvring Settings Table)).