I'm in the tropics. I usually bathe outside, watering the plants at the same time, with a bucket of cold water and a pot to scoop and dump. During cooler times of the year, I bathe in the afternoon or just after sunset, or it gets too chilly for me later. Saves a lot of energy in unneeded water heating, and a lot of water, too.
If I want it warm/hot, I can either bathe earlier and put the bucket of water out in the sun, or use a garden hose that's been sitting in the sun, or heat up the water on the stove, or use hot tap water.
My surround is a flimsy PVC frame with some screws for stability, with thrift shop sheets as barriers (only on two sides; the side of the house and the back yard full of vegetation provide enough screening privacy on the other two sides.)
Yes, the sheets get mildewed over time, but if they are 100% cotton, they can be thrown into the compost. Sometimes I cut off the bottom mildewed portion, then cut the top into smaller rags to wipe up grease on dishes and pots before washing them. I throw the rags away and save soap, water, and time washing dishes that are less dirty or greasy.
I stab the sheet with a knife or cut a notch with scissors to make holes for shower curtain rings. I have some "rings" that are just scrap short lengths of indoor electrical wire (copper, with or without the plastic sheathing intact.) The copper doesn't rust. I also have some old plastic rings I reused.
Sheets are cheap, or you can use ones from your house that are too old or in poor condition.
I do NOT miss having to clean the bathroom, squeegee a surround, or, like a friend used to do, bring a fan into the room on a chair for 20 minutes, to dry it out. Nor do I miss the plumbing headaches and bills with leaks, replacing stems or o-rings, or needing to re-do the entire fixture because they no longer sell parts for your old one.
I change the sheets after a loooooooooooong time. The only other maintenance has been to sometimes scrub some moss off the stone wall next to the area, or re-level the pavers if necessary, or tie the legs to driven-in pipes for stability. My abilities are low, so anyone can do this version!

And it's never collapsed or blown away in a storm.
I still chuckle when a friend wanted to come over to see my "outdoor shower." Later, when I stayed at her home, which looked like the June cover for
House Beautiful magazine, I realized the image she had in her head was probably: woven palm frond surrounds and a fancy rainshower head, bamboo and birds of paradise landscaping and lush jungle vegetation, including monstera winding up the gargantuan banyan trees, with birds chirping as you rinse off after a naked plunge in the pool or ocean.
I can imagine her horror as she saw my ghetto "outdoor shower," with scrap broken concrete paver chunks for a floor, mosquitoes, and leaves I needed to kick aside, after the chickens had been scratching through there, looking for bugs! hahahaha
But like a true friend, she said nothing as I pointed out that the graywater watered the papaya, banana, katuk, ong choy (kangkung, water spinach), ginger, and tropical sunflower, but as I finished, she commented, "Wow, looks like you have a very thorough setup here!"
After I had arrived at her house and saw HER place (albeit without any "outdoor shower"...so there!), I said, "Oh sh!t, I would have never let you see mine, had I known how nice your place is!"
We just had a huge storm over the weekend, and many people were without power for days. I think her area was hard hit, because I haven't had a response to my emails. She's not the type to save rainwater, canned anything, or have a backup water filter, rocket and butane stoves, or other preparedness items.
But she lives in a rural area on another island, so I know the people there will be fine. Her neighbor has a garden, and she's friendly with her sister, so they'd help each other
But she got an example, when she came to my place, of what some people can and DO do, to live in ways more attuned to Nature, and more adaptable when things like hurricanes happen. Maybe now she'll start to put in her own "outdoor shower"...?