Concrete-free Natural Swimming Pool idea

After years of twiddling my thumbs, I finally dived in and treated myself to David Pagan Butler's Natural Swimming Pool e-book plus movie combo pack from the permies digital market. Yes, it may be years before I actually undertake such a project, but it's fun to learn in the meantime to get my cerebral gears turning.

I just finished watching the movie portion this week with my little one. Brilliant! I love that David is so down to earth - quite literally speaking - using salvaged materials and keeping both financial and environmental costs down. In both the movie and e-book portions he's ridiculously witty, and it's always fun hearing him toss puns around with that suave Ringo Star accent.

I'm interested in some feedback on an idea I now have after watching it.

One of the biggest labor-intensive (and I suppose environmentally costly) aspects of the natural swimming pool design is the swimming portion with its concrete block walls. David, of course, shows us in the movie what happens when sandbags were used instead of blocks. The walls provide a nice deep, cool, swimming zone to dive into.

Could Mike Oehler's PSP wall method (like the method he uses in his $50 underground house designs) be used instead to keep that nice vertical swimming portion? Could that be used as a retaining wall to counter the hydrostatic pressure as a concrete-free alternative? Something to think about.