The Germans developed a torpedo which homed in on the high pitched propeller noise made by a high speed escort ship such as a destroyer. Unfortunately, this was similar to the sound made by a U-Boat’s propellers. When they fired this torpedo, the T-5, the U-Boat had to immediately go into a deep dive or the torpedo would double back and hit the submarine.
Charles McCain is a Washington DC based freelance journalist and novelist. He is the author of "An Honorable German," a World War Two naval epic. You can read more of his work on his website: http://charlesmccain.com/ View all posts by Charles McCain