A friend sent me an interesting and useful open source project for making your own recycling shower. It re-uses 10 litres of water in a loop with filtering and heat reclaiming.
Showerloop presentation video:
More technical concept presentation:
Project homepage with extensive build documentation: https://showerloop.org/
GoFundMe fundraiser: https://www.gofundme.com/f/making-the-world-greener