Chris,
Thats an old water well. The water table must be very shallow. We have some like that on one of our places, same kind sandy soil as yalls place.
The strangest thing I have found is this building in the brush. The dogs were bayed up so we kicked the catch dogs out. They caught it in the building. It sounded bad hearing the hog hit the tin... didn't know what was going on. We are guessing its a coyote camp or an old green house...