I have just read that the UK's first public natural swimming pond is being built. It is to be 411 square metres and will accommodate up to 170 bathers. It will be chemical free, with only natural filtration being supplied by hundreds of plants.
Where is this new futuristic idea being built? In the middle of London as part of the Kings Cross Development.

They say "The plants will take time to establish, but we hope by mid-summer swimmers will be able to enjoy the array of beautiful plants, and the variety of insects and wildlife that the zone attracts."
There is also a picture of a woman in her swimming costume wading through the reedy water.

I can think of so many potential problems here, like what happens when it attracts swans or mallards (who will poo in the water, or nest build), what about snakes, foxes and biting insects it will attract? Will it stay clean if humans use it as a toilet too?
I wish I could show you the picture, but you can go to:
www.kingscross.co.uk/kings-cross-pond-club to read more.
It just looks like a big, natural wildlife pond, so I don't get the idea of it being advertised as a swimming pool for humans.