Spray bottom of casserole dish with non-stick spray. Slice potatoes and layer on the bottom of casserole dish, Brown hamburger and drain. Put hamburger on top of potatoes. Mix water with soup and pour over top of hamburger. This can be done in layers. Cover casserole dish with tin foil, make sure it is tightly sealed. Cook 350 degrees for 35 to 40 minutes or until potatoes are fork tender. Double recipe for leftovers, it's even better the next day!