This is coolbert:
Submarine hysteria as we understand it of course not confined to that era of the two World Wars, the Cold War, etc.
An integral part of "invasion literature" as authored by William Le Queux often featuring submarine activity. German U-Boats threatening England, operating surreptitiously, in secret and unannounced. Very sinister like.
"WAR, PROPAGANDA, AND THE FICTION OF WILLIAM Le QUEUX" Reported by Brett F. Woods
"The West is currently engaged in a clandestine war against terrorism and, as fiction follows fact, in the years to come we will doubtless witness the publication of innumerable espionage novels detailing the villainy of Islamic renegades and the corresponding actions of Western society to counter the threat. And while this might be considered as an exploitation of unfortunate events, it is certainly not a new scenario, for the novelist and the spy have long enjoyed a unique and symbiotic relationship with one another."
"Invasion literature" that alarmist type of fiction, the German is coming, invasion imminent, England awash with German spies, saboteurs, "agents".
Those Germans quite often spotted signaling out to sea, their secret messages received by surface vessels OR submarines.
As recounted in: "'THE MYSTERY OF THE GREEN RAY' BY WILLIAM LE QUEUX"
"I looked around me, and saw that we were steaming slowly down a narrow loch, surrounded by mountains which stretched right down to the shores. I looked across the deck and almost shouted out in mysurprise. For there, moving gracefully alongside of us, was a submarine. There were two officers on the deck of the submarine chatting with Hilderman and Fuller, who were leaning over the rail of the Fiona. A submarine! A German submarine in a peaceful Scottish loch! Then this was the secret base we had discussed. I looked up at the wheel-house. In front of it was the very searchlight, with its curious condenser that I had seen in the cavern."
Le Queux it can even be suggested at some point becoming mentally unbalanced, believing his own works of fiction, leading expeditions of faithful readers and followers to detect and unmask all those German "agents" that in reality did not exist.