Why do you think the US Navy needs temperature and salinity data from the South China Sea?
Two answers:
1) They don't, and that's not what the buoys/drones are collecting, or
2) NOAA collects comprehensive oceanographic data all over the world, to track El Nino, or global warming, or fishery-affecting pollution.
The real answer, of course, is that I don't know, and nobody is telling us.