U-22 was a German submarine (U-boat). It was launched on July 29 of 1936. It was used pre-war by the Kreigsmarine for training purposes. In WWII, it was then mainly used for work along the coast since it was small and given its endurance. As a result, it was most useful for operations taking place in the foreboding North Sea. It was utilized against the British coastal convoys, those that particularly sailed along the north east seaboard of Great Britain. It has six successful patrols but failed to return on its seventh after departing on March 20th, 1940. It may have been the victim of a mine, or it may have been rammed by an allied submarine. Some suspect it may even have crashed into a buoy. No one knows for sure. What is known for sure is that its crew of 27 were lost, somewhere in the North Sea.
With a total of 31 vessels sunk, the U-boat U-47 was the most successful of the submarine fleet in the German Navy during World War II. It was launched in October of 1938, two days before Halloween. The submarine had a maximum surface speed of 17.9 knots and a maximum speed of 8 knots underneath the water. It spent 238 days at sea. Among its victims was the British battleship HMS Royal Oak. The boat vanished while on its 10th patrol which began on the 20th of February 1941. It went missing on March 7 of that year. It was thought that it may have been sunk by the HMS Wolverine, but there is no official record of what did occur, although speculation has ranged from mines to a mechanical failure, perhaps being a victim of its own torpedoes, or even a possible later attack. It had a crew of 45 aboard and is thought to have been lost somewhere in the North Atlantic.
There were actually three U-boats that had the U-116 designation. Work commenced on the first one in 1916, but it was never completed and eventually two of the engines were used in another vessel. A second boat with that name was built and launched in 1917. This boat managed to last until just a couple of weeks before the armistice was signed. It was sunk in October of 1918 at Scapa Flow. A third version of U-116 was launched on May 3rd of 1941. It managed to sink only one ship and damage another. It lasted only until its fourth patrol when it sent its last radio message on October 6th, while it was in the North Atlantic at a position of 45 degrees north and 31 degrees west and then was never heard from again. It carried a crew of 56 and all are presumed dead. It is unknown what happened to the vessel.
