25th April 1918
The Imperial German Navy wasn’t having it all their own way in April 1918. At 1.45 AM HMS. Jessamine spotted a German submarine on the surface about 12 miles south of Kilmore Quay, Co. Wexford. She dropped 6 depth charges on the U-Boat and sank her. There was one survivor of the crew of 42- Petty Officer Karl Eschenberg, who was blown through an escape hatch as the submarine went down.
The U-Boat was U-104, a relatively new ship that was commissioned on 12 August 1917. She was on her fourth patrol under Kapitänleutnant Kurt Bernis. Bernis had sunk 8 ships while in command of U-104, the last being SS Fern which was torpedoed 6 miles east of the Kish Lightship on 22nd April with the loss of 13 crewmen. The following day U-104 was attacked by USS Cushing who dropped 15 depth charges and severely damaged the submarine. The crew were trying to repair the damage when they were attacked by HMS. Jessamine.
On 2 March 1918 U-104 had sunk the SS. Kenmare 25 miles north west of Anglesey with the loss of 29 of her 35 crew.
Other U-Boat sinkings around the British Isles in April 1918
11 April UB-33 struck a mine in the Strait of Dover with the loss of all 28 crew.
17 April UB-82 depth charged in the Irish Sea by two Royal Navy trawlers with the loss of all 32 crew.
19 April UB-78 struck a mine in the Strait of Dover with the loss of all 35 crew.
22 April UB-55 struck a mine in the Strait of Dover with the loss of 23 of her 29 crew.
30 April UB-85 foundered off the Antrim coast. All 34 crew were rescued by either HMS Coreopsis or HM Drifter Coreopsis II. Depending on which Wikipedia page you want to believe.