SM U-77 was one of 329 submarine

Submarine

A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has more limited underwater capability...

s serving in the Imperial German Navy (Kaiserliche Marine

Kaiserliche Marine

The Imperial German Navy was the German Navy created at the time of the formation of the German Empire. It existed between 1871 and 1919, growing out of the small Prussian Navy and Norddeutsche Bundesmarine, which primarily had the mission of coastal defense. Kaiser Wilhelm II greatly expanded...

) in World War I

World War I

World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...

, engaged in commerce warfare

Naval warfare of World War I

Naval warfare in World War I was mainly characterized by the efforts of the Allied Powers, with their larger fleets and surrounding position, to blockade the Central Powers by sea, and the efforts of the Central Powers to break that blockade or to establish an effective blockade of the United...

 during the First Battle of the Atlantic.

Operations

U-77. Commanded by Kaptlt. Erich Günzel, lost with her. Came off the stocks at Hamburg (Vulcan) in 1916; in May and June was at Kiel School, and first entered North Sea with U-76 on 29 June, to join the 1st Half Flotilla.

• 5 July 1916. Left for the north, and laid mines between about 57°45′N 2°12′W and 57°47′N 2°23′W. It seems possible she sank in 57°35′N 1°27′W before midnight 7 July 1916 as a result of some accident. Before this she had laid mines off Kinnaird Head
  Kinnaird Head
  Kinnaird Head is a headland projecting into the North Sea, within the town of Fraserburgh, Aberdeenshire on the east coast of Scotland. It is the site of the first lighthouse in Scotland to be lit by the Commissioners of Northern Lights...
  
  .