Im no professional on pools or concrete, come to think of it, I'm not really a professional on almost anything, but I don't think you will have much luck with laying up blocks, I can see very little movement make a block wall crack and leak big time, im like the rest, I would try the shot-crete thing or even a poured wall out of concrete.
And even the shot-crete needs to sprayed against a pretty solid backing to insure integrity and any water sealing properties for any extended period of time, and even more so if you were in an area where there is freezing and thawing going on.
Good Luck!
