i always thought a 1st gen mr2 with an ac motor (regeneritive breaking) would be a good way to go. it has great places to hide batterys, such as where the stock gas tank is, front compartment, back compartment engine compartment and there light weigt so it should be good. the car should be able to be built that would get 100 miles per charge which is way more then enough for an around town car.
as for running the car on water, if it was that easy it would be info thats just out there for free on forums like this one. not on a site thats only exists to get you to enter a credit card.