I only have taken a shower with a friend once during the course of my lifetime.
It was this one time mistake of judgment whereby all of a sudden I was sought after as "husband material" and it really became this pushy rather uncomfortable "confrontational" type of interaction. In the end, she wanted depth and soul sharing with goo goo ga ga all over the place — and I just wanted her to go away.
Needless to say I have declined further showering with those ladies in my life due to memories of this experience.
Today is National Shower with a Friend Day.
It is observed each February 5 annually and is a marketing holiday by New Wave Enviro to promote the use of shower filters.
The holiday was registered in 2014 by a Colorado based manufacturing concern that produces shower filters.
It is a euphemism referencing the showering with a "friend" — which in this instance is a shower head filter designed to reduce chlorine exposure during the cold winter months.
So if you're into shower filtration this day is for you. I suppose if you like company in the shower it is as well. Good luck with this from whatever your perspective.