Unconfirmed reports have suggested a Chinese nuclear submarine has crashed

https://www.taipeitimes.com/News/taiwan/archives/2023/08/22/...

"Defense ministry says no" or "No evidence, says Defense ministry" depending on how you like to interpret it.

They will have hydrophones around this island so thick you could walk across the straights of Taiwan on them, assuming you didn't trip over all the fibre optic cables. It's also geologically active, an earthquake zone and so they're used to both listening, and hearing stuff.