Bubbles.

This is coolbert: 

More research needed. OH good. We are saved. And if so existing technology will suffice.

"US nuclear submarine weak spot in bubble trail: Chinese scientists"

From https://www.scmp.com | Stephen Chen in Beijing | 14 Aug 2023.  https://tinyurl.com/ye25p3pt

"Extremely low frequency electromagnetic signal produced by speeding subs can be picked up by available devices, researchers say"

"The almost imperceptible bubbles could give away the position of most advanced submarines, but more research is needed"

"A study published in one of China’s most respected peer-reviewed journals suggests that advanced submarines could be detected by existing technology, a development that would threaten US dominance of the oceans."

Comments:

* That the normally very security conscious Chinese would allow any of this public surprising?

* Weak spot American submarines [if indeed this be true] also a weak spot for the Chinese?

And Sir Walter! Nice pearl earring!

coolbert.