Very interesting... I really want an amphibious vehicle now.
All the areas I listed have actual TxDOT River Access Roads which are paved and will lead you right to the river. They even have paved parking areas which are just a few dozen yards from the river. They're popular areas for fishermen, kayakers, druggies, AND HUNTERS AND SHOOTERS. You do not need a 4x4 or an amphibious vehicle to access these spots. Just park under the bridge and walk 5-50 yds to the beach.