It seems that there is a place in the South China Sea, a small reef that only has elevation at low tide, a place called Second Thomas Shoal, that is claimed by the Philippines, who has run a retired US Navy ship aground and stationed a small contingent on board to bolster their claim.
China also claims this spot, and has been harassing supply runs to the Philipine contingent. The US Navy recently paid a visit to their brethren on the reef, I'm sure to swap supplies, tell sea stories, and play cribbage.
China took offense, saying that the US Navy has illegally intruded into its territorial water. Yeah, right.