China says it picked up a submarine detector dropped by a US Navy aircraft in the South China Sea

• Chinese state media shared a video of what it characterized as a submarine detection device dropped by a US Navy aircraft.
• The apparent sonobuoy was discovered in the South China Sea near the Second Thomas Shoal. 
• Military maritime patrol aircraft, including China's planes, routinely use systems like these.

China's coast guard found a submarine detection device dropped by a US Navy aircraft somewhere in the South China Sea, a state broadcaster reported.