If you can't take a good shower in 4 minutes, it's a good thing you weren't in the Navy during the Viet Nam unpleasantness. First step, conservation - take a 90 second shower. Second, water hours - restricting the hours you could take a shower effectively prevented a portion of the ship from using because it was on duty time - duty shifts are rotated. Third step, salt water showers only. Soap kind of works like a rock, although some shampoo will sort of foam. Try doing that for 30 days at sea during the summer.