Texas Beaches - this ain't Gulf Shores, Fort Pickens, Myrtle Beach or Daytona. The good beaches are on barrier islands and not strongly developed. More seafront is industrial or wetlands.
A large section of Texas Beaches is part of the Padre Island National Seashore, and open to dry camping, literally on the beach. If you want to chance taking you multi-ton RV onto soft shifting sands.
Texas Beach areas from North to South which is East to West
Sabine Pass (LA border) to Galveston Bay - There is one state park with elec and water. Very isolated. Close to Galveston are two county parks dry camping, and a few commercial parks - never heard anything about the.
Galveston Island -
Sandpiper RV Resort has a good reputation, is frequently used and right on the beach. Also on the edge of the retail part of Galveston.
Galveston Island State Park has two campgrounds - one on the beach, one in the bayside back waters.
I've heard good things about some of the county and commercial parks down the island close to Freeport. Never really investigated them.
Galveston is almost too cool for beach front for me in the winter. And bits of oil washed up from tankers dumping / washing out tanks at the legal limit or the offshore oil rigs doesn't make those good beaches in my opinion. Several people disagree with me.
Not many good beaches or accessible RV areas from Freeport to Matagora Bay.
Small cluster of RV parks near Goose Island State Park near beach at Matagora Bay.
Big clusters of RV Parks in Rockport on mainland side of Port Aransas Bay and over to Ingleside on Corpus Christi Bay.
The north end of Padre Island, Mustang Island and Port Aransas have some very nice places - links from above show you the best. The IB Mcgee Nueces County Parks at the Aransas Channel and the Padre Balli County Park are popular at a cheaper rate. They have stay limits and few amenities, which is to be expected for the cheaper rate. Can't find a working link to those now.
From Corpus Christi all the way down to South Padre right near the Mexico border is the Padre Island National Sea Shore. There area couple mainland side RV parks - don't know if they have wetland or sand beaches on the Laguna Madre or Baffin Bay - some near Kingsville - Some at Port Mansfield.
The "BIG" beach park is at the south end of South Padre right on the Brownsville Ship Channel entrance -
Isla Blanca - a Cameron County park - with 600 full hook-ups sites, monthly rates in three categories - $550-750 per month. Every site is in walking distance to the beach, or fishing along the Ship Channel. But it is also a very active day use park at the beach area. And of course Isla Blanca is very popular. Interested in winter 21-22 - Call NOW.
There is a nearby KOA, a bit more distant from the swimming beach.
The last beach before the border is Boca Chica. I do not think camping is not allowed there any longer. Space-X has their Starship launch facility there, the public access is closed when they are flying rockets.
I've seen on the web that Isla Blanca is a popular place to watch the test flights. A non-orbit test to space is scheduled any day now, with a return to vertical landing at the launch site planned.
Hopefully without the RUD of the last landing. (RUD - Rapid Unplanned Disassembly)