Well, in one sense they are -- but look at the thread: http://www.poolforum.com/pf2/showthread.php?14427

Those aren't aren't like the muddy cow ponds I grew up with, filled with bull frogs, snapping turtles, catfish and pooping cows! Even when I was a kid, I didn't care to swim in those.

On the other hand, I'm planning to call the guys at those companies, and ask. I suspect that those pools wouldn't work that way, if they were transplanted to hot climates like ours.