We are on the same page.....
Best ever example, that I know of, was our subs splicing in a monitoring device in a Commrade Naval installation undersea cable....
Then going back on a regular basis to download the info...years worth.
Balls and know how to do something like that.......and One weasel to give it up.....they would have never known.
I hate spies.
Opening the cable to sea water would be a quick signal to the Sovs that something was wrong.
Of course, sub could have brought along a small chamber in which to work along with a man or two, brought cable in, pumped it dry, spliced in, resealed it, etc....