I have a school project to make a solar water heater. It needs to take sunlight and reflect it onto/into a container that holds water. The surface are of the reflector needs to equal the amount of water in the container. So no giant mirrors heating an ounce of water. How do I do this?

How can a surface area equal a volume? Volume is measured in cubic meters; area in square meters.

When I was a Boy Scout, we made reflective ovens out of flat pieces of aluminum foil folded in the middle. Two of them would reflect on what was to be cooked. A parabolic mirror with the water at the focal point would be a much better reflector.