The concrete is only on the outside of the steel and gets covered up.. its just a footer to hold everything together. We don't have any problems with water under the footer because the bottom of the footer is typically only 36in deep. The bottom of the hole goes to at least 6ft. So water stays in the deepest part of the hole.. this particular pool in the above picture, we actually hit water at 36in deep. But once we dug the deep end, it actually drew all the water down. It was kind of cool to see. I'll get you some more pictures. But if you look through this thread, you'll see some picture of the process of building a vinyl liner pool.