Natural swimming pools

In researching design options for clients over the years, I've looked into what's involved in building natural swimming pools -- that is, ponds that stay safe enough for swimming without the use of chemical inputs. Here are some of the best links I've found on the subject:

Organic Pools DIY Manual by David Pagan Butler (PDF, 1.2 MB, 2013)

Build Your Own Natural Swimming Hole by Douglas Buege and Vicky Uhland (Grit Magazine, 2007)

The Ultimate Guide to Natural Swimming Pools by Lorena Romo (Porch, 2021)