It is easier in tropical countries like Colombia, where “cold” is basically “warm”. In colder (northern) countries, I tried this but it is very hard because “cold water” (i.e., non heated) is way too cold (like minus temperatures).
I agree cold, hot, warm are all relative. Somewhat related I've seen people from hot countries worry about "cold weather". To them ~20C is cold compared to 35C hot day and was blamed to be the cause of colds and flu. Often perpetuated in movies and TV too a tired old trope. So yes to someone in a hot country a "cold" shower may be considered warm to someone from a cold climate.
My record for cold shower temperature was 39.9F (4.4C), here in New York City. Five minutes at that temperature bordered on pain. My fingertips turned purple.
The warmest cold shower I took was in Brazil. Sadly, I didn't get to enjoy it because I was sunburned.
Nitpick: it is difficult to take a shower with water in solid form (ice).
> Nitpick: it is difficult to take a shower with water in solid form (ice).
Nitpick: having a temperature below zero does not necessarily mean that it is in a solid form; for example, it could be at a high pressure or not have a nucleus to freeze around (supercooling).
Bonus points if you can scale it up to a mannequin.
The first, pounding it inside the sealed bottle, is creating some sort of disturbance to crystalize around (an "unsuspecting nucleus"), and the second is pouring it semi-shower-like.
I do think it would be interesting to see it, though.
But I guess it depends on your knobs shower knobs.
Seems really warm!