When we go camping, we try to reproduce the experience with a Sun Shower, which is just a plastic bladder with a show nozzle attached, that we hitch up to a tree limb. It holds five gallons of water and heats up amazingly fast if there's any sun around. What really amazes me is that we can both shower with a shared five gallons of water, once we learned not to dilly-dally.
We have low-flow showers in our house, but I can guarantee we use far more than two and half gallons of water, even when we try to move fast. I also love soaking in a hot tub of water at the end of the day. I hate to even think about how many gallons of water that uses.
So even though we don't live in a palapa anymore, and we don't have a white sand beach or an ocean to gaze at, we are setting up an outdoor bathing and soaking space, in the interests of water conservation and for the pure pleasure of bathing outside, in nature, under the sky.
It's solar heated and pumped, with a UV filter. If there's anything we have plenty of in Texas, it's sun, so the water gets as hot as we want it to. The barrel is from Snorkel Tubs and the solar pump and various components are from a dozen different solar power vendors.