Andrew Jennings
this is the problem with submarines. Over 20 years it is possible to develop a whole new way of finding them, even in deep oceans https://interestingengineering.com/military/chinas-sensor-detect-hidden-us-nuclear-submarines #AUKUS #auspol
China's sensor could detect hidden US nuclear submarines using gravity

Chinese researchers have built a compact gravity sensor that measures tiny mass changes, with the potential to detect submarines at sea.

Interesting Engineering
Apr 5 at 8:22amWeb