We are thinking more in terms of an in-ground pool. I noticed these are made of different materials -- concrete, fiberglass, and vinyl liner (in order of decreasing cost). Can anyone comment on pros and cons of the different materials? It may be a moot point for us, though, as there aren't many houses with pools for sale in the area we are looking -- seems to be just half a dozen on the market at any one time in our price range.