With 4 long haired teenagers I'd surrender! Actually, maytrix is right, a little fresh water rinse, some suds then rinse. Doesn't use much water. Didn't they call that a Navy shower? If you anticipate at least 4 20-30 minute showers a day you should be asking where to stop for water. Like they said in the other post it's easy to get water in the BVI and not expensive.

What amazes, and bugs me personally, is all the hair that builds up in the cockpit after all that brushing/combing. You might advise them to try to do that on the sugar scoop as much as possible.