SM U-93 was one of the 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...

.
U-93 was engaged in the naval 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...

 and took part in the First Battle of the Atlantic.

Since Feb. 1917 she was commanded by the late author of books (e.g. U boat 202. The war diary of a german submarine, 1919) and experienced submarine commander Edgar von Spiegel von und zu Peckelsheim

On 30 April 1917 about 180 miles south of Ireland, in the Atlantic, German U-boat U-93 attacked HMS Prize

HMS Prize

At least one ship of the Royal Navy has been named HMS Prize including a Q-ship of World War I; see William Edward Sanders....

, a three-masted topsail schooner (one of the Q ships) commanded by Lieutenant Sanders (who received a Victoria Cross

Victoria Cross

The Victoria Cross is the highest military decoration awarded for valour "in the face of the enemy" to members of the armed forces of various Commonwealth countries, and previous British Empire territories....

for the action). HMS Prize was damaged by shellfire. After the 'panic party' had taken to the boats and the ship appeared to be sinking, the U-boat approached to within 80 yards of her port quarter, whereupon the White Ensign was hoisted and the Prize opened fire.

Within a few minutes the submarine was on fire and her bows rose in the air, whilst the Prize was further damaged. The U-boat disappeared from sight, and was believed to have been sunk by the crew of the Prize and by several of the German crew (including her captain) who had been blown or jumped into the sea.

Amazingly, neither of the crippled ships had sunk, with the Prize being towed in flames back to Kinsale, while the U-93 struggled back to the Sylt nine days later after a dramatic escape effort through the British mine and destroyer barrages off Dover.

U 93 after repairs operated in the English channel. She was lost after January 15th, 1918 of unknown reasons.