I am sensitive to the U-Boat thing as I live on the North Carolina coast very close to Cape Lookout which is part of what was known as the most dangerous waters in the entire World during 1942.
Ships were torpedoed within sight of land here very frequently in those days.....particularly tankers.
Millions of gallons of oil washed up along the shoreline along with bodies, empty lift boats, and other wreckage.
The wrecks make for good fishing and diving these days.