The transom shower is my first choice. Our head is so tiny I can't stand up
straight in it. We have hot and cold water on the transom and if you're just
out for the day the hot is still quite warm. When we bought the boat I
thought it was silly but now it's a lovely luxury.

My second choice after our own boat (which does carry 400 gallons of
water so it's not like we have to conserve much even in the Bahamas
although we do) is to swim and then shower on deck (assuming warm
weather). We have a pressure fresh water connection on deck, and it
doesn't need to be hot water in warm weather. I wear a bathing suit
if there are people around for fear of striking them blind.