You know, I had know idea that this was where this was happening. I thought it was part of that dispute with Japan over the Senkaku Islands.
Geographically, this is insanely aggressive. In effect, they are claiming hegemony over all of southeast asia.
Heck..China's building artificial Islands in the disputed zones...here's the airplane runway on one of those Islands....When in operation it will be able to "accommodate almost any type of aircraft that China would want to land"....Before this construction China lacked the refueling and resupply capabilities to reach the southern part of the South China Sea.... These Islands are being seen as part of an attempt to assert China's territorial claims by establishing physical facts in the water.
Now if you look at China's New Silk Road for trade you can see why the South China Sea is so significant....not just militarily and for the gas and oil reserves there, (which have great meaning for those nations disputing with China), but the trade routes themselves.