If you want to have pressurized water for a shower or a quick rinse of the boat without wasting water and/or electricity, this is an idea I copied from a cruising couple on a Moody 376. It's a plastic tank found in gardening stores and is used for spraying water and/or chemicals. The only change I made is to fit a couple of quick-disconnect fittings and a shower head. You fill the tank with water of the exact temperature you desire and pump the handle several times to create pressure (there's also a pressure-relief valve if you pump too enthusiastically). The flow is very impressive and the contents last for two shortish showers or a single, more luxurious one. Since it's portable, you can shower in the bow and not disrupt anybody sitting in the cockpit; you can even give your sails or deck a quick rinse (that's how the cruising couple used theirs). As a bonus, you have total control of how much water you use.