Basically, I bought a 12V water pump and attached it to a cigarette lighter power plug. I use the pump to pump water from a 5 gallon storage tank to a hand-held shower head. The idea is that I fill the tank with hot water from my bathtub before I head out surfing, I put the tank and pump in my car trunk, and, after I'm done surfing, I plug in the pump and shower off with the water from the tank. By the time I'm done surfing, the water should have cooled to a pleasant temperature.
I've tested the electrical work and full system test to come soon!
Here's a pic of the work area while I was putting it together:
Surf shower v1.5. The water system test was a success! The pump has quick-connect plugs to which you attach the hoses. Mechanically, they are rather fragile. To protect the quick connects, I've mounted the pump inside a rubbermaid tub and used electric conduit clamps padded with a bit of neoprene to guide the hoses so that the hoses can flex and move around without straining the connectors. I also mounted a lighted power switch on the other side of the tub. I used a copy of the disappointing 'The World is Flat' book as a backstop for the drill and cutting board for the neoprene.
I've been using the shower regularly after surfing and it works wonderfully. The 5-gallon tank has turned out to be a good size. Most full-flow shower heads flow at a rate of 2 to 2.5 gallons-per-minute. So a 5-gallon tank (which weighs 40 pounds, when full) will last a bit over 2 minutes of continuous usage. I find that by turning off the water switch on the shower head while I soap, I end up using about 3 to 4 gallons of water, and usually have plenty left over at the end.
Here's the final setup:
The water flows out of the resevoir, through the strainer (the black circular device attached to the tube), to the pump, then from the pump to the hand-held shower head. There is a lighted rocker switch mounted on the right side of the tub.