They aren't spying on "undersea cables". They aren't sending subs down to split fibers or plant taps. Those days are long gone.
They are perhaps tapping at point where cables leave the shore, but even that is old hat. With everything being encrypted, and the sheer volume of traffic, intel agencies these days find it much easier to go to the source. If the NSA or China want to read your email, they don't tap undersea cables. They go directly to your email/text/cell service and siphon only the data they want. Or, for things like meta data/location tracking, they can just buy the data like any other company. That is the real future: the commoditization of espionage.
They are perhaps tapping at point where cables leave the shore, but even that is old hat. With everything being encrypted, and the sheer volume of traffic, intel agencies these days find it much easier to go to the source. If the NSA or China want to read your email, they don't tap undersea cables. They go directly to your email/text/cell service and siphon only the data they want. Or, for things like meta data/location tracking, they can just buy the data like any other company. That is the real future: the commoditization of espionage.