In a large bowl, add the water and the salt and stir to combine. Add the chicken breasts to the bowl and let them soak in the salt water for 30 minutes. They'll be fine sitting at room temperature since the water is ice cold (unless it is very hot in your house-- then put the bowl in the refrigerator). After 30 minutes of soaking, drain the water and rinse the chicken under cold water.
Preheat the oven to 400°F. Spray a 9x13-inch pan with nonstick spray.
Coat the chicken breast with olive oil, and place them into the pan.
In a small bowl, combine the garlic powder, rosemary, salt and pepper. Sprinkle the spice mixture evenly over the chicken breasts.
Bake for 25 minutes, or until the internal temperature of the chicken reaches 165 degrees F. Allow the chicken to rest for a few minutes before slicing.