Set your oven to 425°F and grease a 13x9-inch baking dish with nonstick spray.
Combine the uncooked pasta, marinara, water, salt, pepper, and diced chicken directly in the baking dish or a large bowl and mix well.
Cover the dish tightly with foil so moisture won’t escape, then bake it for 30 minutes.
Remove the foil and stir the pasta; it’ll be firm with some liquid still present.
Sprinkle shredded mozzarella evenly on top, then add the Panko breadcrumbs and grated Parmesan cheese.
Return to the oven uncovered and bake for another 10 to 15 minutes until the cheese melts, the top browns, the chicken is cooked, and the pasta is tender.
Let cool slightly, garnish with fresh herbs if you like, and serve warm.