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 island, but the exact location was not disclosed. “The key point isn’t that a Chinese destroyer was observed; it’s that a relatively inexpensive commercial platform was able to do it,” said Ray Powell, director of Stanford University’s SeaLight Foundation. So far, the Philippines has not reacted to the latest incident, while the Chinese foreign ministry has said only that the People’s Liberation Army Navy’s activities complied with international law.