Preheat the oven to 350°F and lightly spray a 9x13-inch baking dish with nonstick cooking spray.
Peel and slice peaches. Add peaches to a medium sized pot and add water and 1/2 cup sugar. Cook over medium-low heat until peaches are soft (10 to 15 minutes).
Remove from heat and strain peaches into the prepared dish. Add 1/2 cup of liquid remaining in pot over peaches.
Sprinkle with boxed cake mix.
Top cake mix with 1/4 cup sugar and 1/4 teaspoon cinnamon.
Using a butter knife, make swirls in baking dish to combine some of the dry ingredients with the peach juices below.
Drizzle with melted butter.
Bake for 30 to 35 minutes, or until the top is golden brown and set.