Preheat the oven to 400°F (200°C).
In a shallow bowl, combine whole wheat breadcrumbs, grated Parmesan cheese, garlic powder, dried Italian seasoning, salt, and black pepper.
In another shallow bowl, whisk together the eggs and water until well combined.
Pound each chicken breast to an even thickness of about 1/2 inch using a meat mallet or rolling pin.
Dip each chicken breast into the egg mixture, allowing excess to drip off, then coat thoroughly with the breadcrumb mixture. Press the breadcrumbs onto the chicken to adhere well.
Heat olive oil in a large oven-safe skillet over medium heat.
Add the breaded chicken breasts and cook for 3-4 minutes on each side, or until golden brown.
Remove the skillet from heat. Spoon marinara sauce evenly over each chicken breast.
Sprinkle shredded mozzarella cheese evenly on top of the sauce.
Transfer the skillet to the preheated oven and bake for 12-15 minutes, or until the chicken is cooked through (internal temperature reaches 165°F) and the cheese is melted and bubbly.
Remove from the oven and let rest for 5 minutes before serving.