SM UC-78 was a German Type UC II

German Type UC II submarine

Type UC II minelaying submarines were used by the Kaiserliche Marine during the World War I. They displaced 417 tons, carried 7 torpedoes and up to 18 mines...

 minelaying

Minelayer

Minelaying is the act of deploying explosive mines. Historically this has been carried out by ships, submarines and aircraft. Additionally, since World War I the term minelayer refers specifically to a naval ship used for deploying naval mines...

 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...

 or U-boat

U-boat

U-boat is the anglicized version of the German word U-Boot , itself an abbreviation of Unterseeboot , and refers to military submarines operated by Germany, particularly in World War I and World War II...

 in the German Imperial Navy  during 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...

. The U-boat was ordered on 12 January 1916 and was launched on 8 December 1916. She was commissioned into the German Imperial Navy on 10 January 1917 as SM UC-78."SM" stands for "Seiner Majestät" (His Majesty's) and combined with the U for Unterseeboot would be translated as His Majesty's Submarine. In 12 patrols UC-78 was credited with sinking a single ship, either by torpedo or by mines laid. UC-78 was rammed and sunk by the British steamer west of Cherbourg on 9 May 1918.