I saw a really nice one in costa rica. It routed the water through a 55 gallon
black plastic drum that was up above the shower to give it some pressure. the
thing was filled off of rain gutters, and within a couple of hours, the water
was nice and warm, but cool enough to refresh you. Really the only way to
clean off after a "hard day" on the beach!

the one they had didn't even have a shower head, just a spigot and hose with
one of those "soaker heads" you hook on to your garden hose. still, it was
glorious to soak your head under that thing after being cooked out in the sun
all day.