Okay, here’s the thing though. It isn’t a question of if. They existed and this is exactly what they did.
After the United States entered World War II at the end of 1941 and Germany subsequently declared war upon it, Great Britain recommended several steps the United States should take in order to safeguard their ships from Nazi u-boats. Recommendations included sailing ships in convoy (preferably with escort, but records proved ships in convoy without escort were still safer than ships sailing alone), if a ship had to sail on its own, it should avoid known navigation routes and markers, and towns and cities along the East Coast should adhere to strict blackouts at night. These recommendations came from the previous two years of experience in which u-boats absolutely ran wild in the North Atlantic and North Sea, obliterating British shipping. This period of time was referred to by Nazi u-boat captains as “The First Happy Time”.
Despite British warnings, the United States was slow to follow them and impose restrictions. Ships continued to sail along marked navigation routes and run standard navigation lights at night. Boardwalk communities along the coast were only requested they turn off their lights at night and the cities weren’t even asked that because they didn’t want to offend the tourism, recreation, and business sectors.
Blacking out coastal communities would have made it infinitely harder for Nazi submarines to find and sink targets. A ship running with no lights is still visible against the backdrop of a lit city.
Conversely, a dark ship running against a dark coast is virtually invisible.
But because citizens living on the coast refused to adhere to wartime suggestions for amenity reasons, merchant ships sailing up and down the East Coast became sitting ducks of u-boats. The US government did not begin strictly enforcing blackouts until roughly August 1942. By then, the Nazis had been given 8 months to run rampant along American shores. This time period was referred to by u-boat captains as “The Second Happy Time” or “American Shooting Season”.
By August, Nazi u-boats had sunk 609 merchant vessels, totaling 3.1 million tons and costing thousands of lives, mostly of merchant mariners performing their essential jobs.
By comparison, only 22 u-boats were sunk.
While the failure of coastal blackouts were not the sole reason the Nazis had such success during this time period (the Navy was slow to implement convoys and remove notable aids to navigation along the coast), I do not think it can be argued they did not contribute significantly to such great loss of American lives.
