Nothing new. Back in the late 70s I had a similar device called Solar Shower (IIRC).
A 2 gal. plastic bag built exactly like that one. Clear plastic on one side, black on the other. It had a tube and sprinkler type nozzle.
Laid on the sunny deck of my sailboat the water would get way up the the hundreds in an hour or so.
We hung the ‘shower’ bag on the boom over the cockpit and took hot showers.
Terrific little device.
We have one that we use on our sailboat. Hubby and brother use it after diving. They work great.