This is a great idea
I go swimming in a lake nearby that is in a moderate to major point of pollution. People obviously don't care about the environment, which is there is so much trash in certain areas. The bottom of it is sludge and debris, but I always consider swimming in a natural pool is better in some way. I would think that this is a good idea. When I lived in my other house in the country before my parents got divorced, we had a ditch that we would swim in on hot Summer days, as well as some nights because the water was usually warmer. When it was starting to become winter, they would stop the water flowing and there would be puddles with many species of fish inside of them. Rather than leaving them there to freeze, I set up a small pond inside of our garage. When spring came, I released them in the lake that I mentioned and made sure it was ok for me to do so before I did. The fish that I kept were native to that lake so it gave me a good sense that it was a good idea. Since I currently no longer live in the country, I do my best to save the lives of fish by keeping an eye out on some nearby canals. Last year, I did the same, except I went to a canal and the fish were much bigger. I did my best by saving a majority of the young fish and I also got 4 axolotl's and about three gallons of scuds. I released a majority of the things I caught, but I kept the scuds to feed my fish( some sun dried, some alive). Overall, chlorine pools kill my hair and my skin, so I hate swimming in them and I never would say no to swim natural.