Soon Scarborough Reef (or Shoal) only 140 miles (220 km) from Manila Philippines, may be added to the list of new Chinese island air/naval bases. A SeaWeb sensor line may also be strung between Scarborough and the large Chinese base island of Hainan (see red dashed line on the map below).
Large Australian, US or Japanese UUVs could perform and intelligence gathering tasks required near the Chinese coast. Such UUVs could be submarine, ship launched, air-dropped. They could also be launched from friendly coasts or islands in the region. Being much smaller than subs UUVs are harder to detect. And no crews to lose.