You could always come over and shower on MY boat!
Sorry ........ couldn't resist it!
I have used several versions of solar
showers for camping and on boats, and have found them very successful. A simple tank on the coach roof, painted flat black, with a hose and shower head
attached works well in the Florida
The hot water on demand idea also sounds good - I assume you would use propane
? Shower curtain optional (we live in a cosmopolitan world, don't we?)
It would be more cramped, but it might also be possible to rig a "sit-down" shower on your porta-potti, with or without a small shower sump.
All in all, I would go for a solar bag on the roof, hoisted into the rigging
whenever your feel dirty. The cockpit
is a great place to take a shower!