Which was part of a plan to raise a sunken Russia nuclear submarine. I remember a short TV documentary which promoted the cover story that they were planning to mine manganese nodules. Interestingly, there are many stories of the period to the effect that there were spies in every port in the 1970s and anyone who was doing anything suspicious (like L. Ron Hubbard and Scientology) was likely to have trouble.
The US is said to have a submarine that can cut into undersea cables and install a tap which is no small feet because there is a dangerous high voltage cable to power undersea signal repeaters in them.
they didn't cut the cable but wrapped something around it that got a signal by induction. Works in an electrical cable because the different wires are deliberately wound at varying pitches to minimize crosstalk, but you gotta cut to get into an optic fiber cable. It was a brilliant piece of signals intelligence that was countered by human intelligence, the device is in a museum, one of many in Russia that I'd like to go to but never will.
