Comment by discodave

https://en.wikipedia.org/wiki/SOSUS

Both the US and China have newer more advanced capabilities than a 50 year old system...

> [SOSUS] was the primary cuing system that antisubmarine forces used to localize and potentially destroy targets for over forty years, but secrecy largely kept that fact from the fleet. The lack of strong fleet support was a factor when budget cuts after the Cold War fell heavily on the surveillance program.

Driving cars down every street in every advanced country to take photos seems ridiculous, but Google did it (StreetView) and the US DoD has more money than Google...