solar water heater

Don, get a 10-liter Dromedary bag from the nearest MEC store. Buy also a "shower head" with tubing that screws in place of a regular Drom spout, same MEC store. Hang it onto the nearest tree on or any hook on the South-facing wall of your rig. The Drom bag is black, and will become pretty warm under the sun, warm enough for a shower. Total cost about 40 bucks. There are other fixtures that work too, similar to garden spray with manual pump and they probably have more gallons, but with bag on the hook the gravity does the job. Also, the bag is compact when not in use. 10L = 3 gallons, but the shower head is tiny so it works. It's not for relaxing half an hour in the shower - but it works for one man to wash the hair and rinse the sea salt off. Or you can hang another bag next to the first one. It is of course an exterior shower - no privacy.

This solar heater in the link reminds me 2 things that I saw and voted against: small solar desalinator made in Australia, and solar fountain (with solar pump, same as this heater).

The first one is similar to that "solar heater", only more channels and arrangements for collecting the vapor. Aluminum with polycarbonate cover - very similar. Expected to last less than 10 years due to build-up of cr-p from the water, and deterioration of polycarbonate.

The solar fountain works only occasionally - when there is a sun. No sun - no pumping.