[AzCal Retred]

A lot of warships in that part of the world in recent years have been disabled and rendered combat ineffective in "accidental" collisions with commercial vessels. Who needs to field their own warships when you have all these commercial vessels available to ping off of an adversary? Most ships in open ocean run under autopilot. All warships have savage amounts of listening & detection capability, most have auto-avoidance circuitry. Maybe someone's exploiting a vulnerability?
https://www.nytimes.com/2017/08/20/world/asia/uss-john-mccain-collision-merchant-ship.html
https://www.nytimes.com/2017/06/16/world/navy-destroyer-is-damaged-in-a-collision-near-japan-and-seven-sailors-are-reported-missing.html?action=click&contentCollection=Asia%20Pacific&module=RelatedCoverage&region=Marginalia&pgtype=article

https://www.bbc.com/news/world-asia-56000531
The commercial ship was not damaged in the incident and felt no impact from the collision, Japan's chief cabinet secretary Katsunobu Kato said. Not much is known about the vessel but local reports say it was registered in Hong Kong.

https://www.naval-technology.com/projects/sssoryuclasssubmarin/

[Karl Fenn]

Perhaps they have developed a communication jamming system and are trying initial experiments, all very space age.