Comment by underseacables

If you find this interesting, I highly recommend the book "Blind Man's Bluff: The Untold Story of American Submarine Espionage".

The book discusses "Operation Ivy Bells" whose mission was to tap the underwater Soviet communication lines during the Cold War. The submarine installed a recording pod onto Soviet cables and recorded everything.

How did they find the cables?

A technician told a story about growing up on the Mississippi river, and how you could often find a sign on the bank, telling you that there were underwater cables. He hypothesized that the same thing might exist in the Soviet union.

Sure enough, the submarine secretly crept into Soviet water, popped the periscope, and found a sign in Russian on the bank, saying be careful, underwater cables.

It's rumored that when the Soviets learned of this, they went down and found the pods. During disassembly, they found a stamped plate deep inside which read "Made in the USA."