While visiting Padre Island National Seashore, I tent camped right on the beach. Being so close to the water and camping on the sand was terrific. Unfortunately, the wind that we encountered was not. After returning from a day excursion to Corpus Christi, we found that the wind had completely decimated out tents, snapping poles and burying our personal effects in sand. Thus, if you wish to camp on the beach at Padre Island National Seashore, it is probably best to do so in a recreational vehicle or camper.
Signs along the Grasslands Nature Trail advise hikers that Diamondback Rattlesnakes can be encountered in the grassy dunes. We would have loved to have seen one, but didn't. Mosquitos can also be a problem, as well as the brilliant South Texas sun. It may be a good idea to bring sunscreen and bug dope. Also, Seashore literature warns of Portuguese Man-of-war and Sting Rays in the shallow water. None of these things are really a reason for undue concern, but good to be aware of.