Probably have to contact TPWD on that one. From a black and white perspective you're in the lake and not in the state park. But of all things I in no way can imagine someone getting nailed for walking out into the water to cast... Now if you're talking about going into the water and wading down the bank say fishing for spawning crappie, you're wading down the bank and especially if you go to an area that's in front of land not the park, I could see that more likely. Going waist deep to cast out a catfish line or something like that? I'd have a dropped jaw if I saw a ticket for that.