https://en.m.wikipedia.org/wiki/Countercurrent_exchange https://en.m.wikipedia.org/wiki/Countercurrent_exchange A lot of mammals do this including humans. Don’

https://en.m.wikipedia.org/wiki/Countercurrent_exchange https://en.m.wikipedia.org/wiki/Countercurrent_exchange A lot of mammals do this including humans. Don’t know if there’s a drop in plumbing shower solution.