Here is the Ro/Pax ferry Bang Chui Dao under construction in 1995:
The ferry site,
Now equipped with ramps to launch and recover amphibious vehicles at sea:
With all the videos of this operation available on CCTV it should be no problem to copy this on the many RoRos in the US fleet.
Cheaper than to built a fleet of new Landing ships:
China appears to have other options as well_
Letting people know in advance is the only civilized way to conduct an invasion IMO.