Preheat the oven to 350 degrees. In a 9-by-12-inch baking dish, spread the tomato sauce evenly across the bottom of the pan.
Combine the egg and water together in a bowl. Then, to bread the eggplant, coat both sides with flour, followed by the water and egg mixture, and then the breadcrumbs. Lay a few slices of eggplant on top of the sauce. Cover the eggplant layer with some of the mozzarella. Layer more sauce on top of the cheese and repeat for 3 layers, or until your ingredients run out. Sprinkle parmesan cheese over the top to finish. Place the dish in the oven and let bake for about 30 minutes, or until the cheese is slightly browned.