Set the oven temperature to 350°F and grease a 9x13 baking dish with cooking spray.
Spread the uncooked rice evenly in the dish, then sprinkle 1 cup of shredded cheddar cheese, salt, and pepper over the rice.
If your chicken breasts are thick, slice them in half lengthwise or gently pound them to an even thickness for uniform cooking.
Arrange the chicken breasts over the rice layer.
Dot the chicken and rice with spoonfuls of the cream of chicken soup.
Pour the water over the entire casserole, then sprinkle the onion soup mix on top.
Place the dish in the oven uncovered and bake for 1 hour.
Take the casserole out of the oven and stir the extra sauce into the rice.
Top the casserole by sprinkling the remaining 1/2 cup cheddar cheese before serving.