U 104 departed on her last cruise around 11 April 1918 from Wilhelmshaven. She sailed northwest, passing to the north of Shetland and headed to the area west of the Hebrides, subsequently west and south of Ireland into the Irish Sea. Two ships were torpedoed before U 104 itself was sunk, near location 51°59'N 6°26'W.
In the early hours of 25 April 1918, HMS Jessamine sighted U 104 and attacked with depth charges. These damaged the submarine, but as the crew attempted to open an escape hatch only one crew member escaped through being blown out by escaping air. The others were pushed aside and drowned by the water rushing in. The survivor was picked up by HMS Jessamine three hours later.
The survivor was engine room petty officer Karl Eschenberg, from the Westphalia area of Germany. There were 39 other members of crew, commanded by Kapitän-Leutnant zur See Kurt Bernis.
The above paragraphs were summarised from the interrogation of the survivor, Karl Eschenberg.
U-boat 104 had been in service for only five months at the time of the attack on the Kenmare. U-104 sank a total of eight ships, which accounted for a third of the number of ships (25) sunk by its commander, 32-year old Kapitän-Leutnant zur See Kurt Bernis, until he was killed in the sinking of his U-boat on 25 April 1918.
On 23 April 1918, U-104 was attacked by USS Cushing using depth charges. These damaged the submarine. Two days later, HMS Jessamine came across the submarine on the surface in St George’s Channel as its crew were attempting to repair the damage, caused by the depth charges. KLt Bernis dived his submarine, but depth charges from HMS Jessamine forced him to surface. The U-boat was finally sunk, taking 31 to the bottom with her. The location of the wreck of U-104 is shown on this map, supplied courtesy D.J. Grundy, and compiled using data from www.wrecksite.eu.
Further information, with correspondence to and from the widow of crewmember Könnecke, on this link.
The images below show a model of U-boat 104. It is on display at, and the images are supplied courtesy of National World War I Museum, Kansas City, MO, USA.