Lemp died in 1941 when the U-110 was sunk by British ships. The exact details of his death are somewhat controversial. Officially, Lemp drowned, but it has been alleged that he was shot to death by the British.
Lt. Fritz-Julius Lemp commanded the U-30 during World War II. In January 1939, Lemp ordered the sinking of an American luxury liner, the Athenia, believing it to be an enemy ship.
The German government, fearful that the U.S. would be provoked, ordered the truth covered up, and blamed the sinking on the British government. Although Lemp received a firm chewing out from Admiral Karl Dönitz (who assured Lemp that several prominent officials wanted his scalp), he was not relieved of duty.
Later in 1939, Lemp's boat was assigned to carry an experimental new device for field-testing: A schnorkel, or a tube extending up to the surface that allowed the boat's diesel engine to be operated at depths up to about a hundred meters. This allowed faster cruising while submerged, less use of the batteries and more time for said batteries to charge before deep dives, and made detection by enemy spotters much harder. Despite all these advantages, Lemp was not enamored of the device, which was prone to malfunction. He realized that the Kriegsmarine's choice of his boat to test the experimental device was in large part punishment for the Athenia incident.