Small commercial sea drones that have shown they can monitor PLA warships in the South China Sea have emerged as a new potential challenge for Beijing in the disputed waters.Last week, Seasats, a California-based autonomous vessel maker, released footage – which has been verified by Reuters – showing its Lightfish drone operating near a Chinese Type 052D guided-missile destroyer on June 16.The latest encounter reportedly took place 105km (65 miles) northwest of Luzon, the largest Philippine...