Our RV build ("Mad Maxine") will have a recirculating shower to allow for nice long, hot showers without using our fresh water supply (although it will allow replenishment from the fresh water tank as needed).
This is the first mockup to test the premise and determine if it will work. We learned a lot and will be making some minor modifications (mostly to accommodate the bathroom sink and bidet - they will both use "shower water" but won't be recycled back through - hence the automatic makeup from the fresh tank)