One if the nicest RV resorts in Texas is just north of Corpus Christi on the coast - Gulf Waters (just south of Port Aransas).
Port Aransas TX Texas USA US Gulf Waters RV Park Beach Front Resort Community Corpus Christi
Across the bay on the mainland in Aransas Pass is Ransom Road Ransom_Road_RV_Park
. Not on the beach, but still very nice. There are many other parks in this general area, but these are two of the nicest.
Moving up the coast, when you get to Galveston Island, perhaps the nicest resort there is Jamaica Beach RV Resort Jamaica Beach RV PARK
. It is not "on the beach", but the beach is across the street. If you want "on the beach", you can go to Galveston State Park, but it's not is such good repair these days.
As you head further east, the pickings get slim, since IKE took out most of the camping on the Bolivar Pennisula, although a few places have reopened.
As you move further east, it gets more industrial and many of the parks are filled up by fivers housing contract personnel working in the plants. You might check out this RV park on Pleasure Island at Port Arthur Pleasure Island RV Park in Port Arthur, TX
, but the beaches are not like you will find south of Corpus Christi or over in the Florida panhandle.