China dropped a dozen underwater drones, also known as unmanned underwater vehicles, in an unspecified location in the South China Sea to carry out “scientific observations,”according to state-run media outlet Xinhua. The torpedo-shaped vehicles — called Haiyi, or sea wings in Mandarin — will remain underwater for a month, according to reports.

 

https://www.cnbc.com/2017/08/12/china-uses-underwater-drones-in-south-china-sea.html