Dave, I noticed in my research that "tank" was on the way out. As a 6 year old I remember thinking that was a misleading name.
This place is in a very rural area north of Groesbeck, TX.

I have no idea why hogs avoid the small pond. It is hidden in trees and they wallow on the edges very lightly. They are practically destroying the banks of the 20 acre lake although shooting pressure buffers it some.
I study and monitor the hogs and wildlife at all times as the place is partially in wildlife management status with the state.
My guess is that they like more sun exposure so that the mud cakes quicker on the skin. This pond is surrounded by trees. I is only 3 feet deep at one point and is average 1.5-2 feet I guess. It is a stunning little pond full of life. The shade allows it to resist drying up.