China’s Newest Nuclear Submarine Sank

[steve58]

Not quite 'current', but

WASHINGTON—China's newest nuclear-powered attack submarine sank in the spring, a major setback for one of the country's priority weapons programs, U.S. officials said.

The episode, which Chinese authorities scrambled to cover up and hasn't previously been disclosed, occurred at a shipyard near Wuhan in late May or early June.

https://www.wsj.com/world/china/chinas-newest-nuclear-submarine-sank-setting-back-its-military-modernization-785b4d37?st=Ue9xdm&reflink=desktopwebshare_permalink

[Sir Slash]

I thought they were supposed to sink. And then come back up again...Ok, now I got you. 

[JasonPratt]

They probably built the boat with hollow concrete pylons, using a substandard cement mix. And the hollow centers were filled with trash glass.

China has A LOT of experience doing that, though, so by now you'd think they'd be competent at it.