We've cruised the San Juans for two years now. We find that it's best for everybody to tie up to a dock every other day. We shower then, and don't use the shower on the boat much.
Generally, we, and the previous owner, use a Sun Shower sitting on the deck and dropped through a
hatch into the head compartment.
Our boat has hot water, but only after being plugged into the dock or running the engine for a while.
It's nice to have, though.
But not a huge deal, I think. It's hard to work up a sweat when it's 60 degrees and raining!