Preheat oven to 350°.
Combine 1 1/2 cups cantaloupe and water in a blender, and process until smooth. Combine pureed cantaloupe, cake mix, eggs, and oil in a large bowl. Beat with a mixer at low speed 30 seconds; beat at medium speed 2 minutes. Pour batter into a 13 x 9-inch baking pan coated with cooking spray. Top batter with remaining 1 1/2 cups cantaloupe, lightly pressing cantaloupe into batter.
Bake at 350° for 30 minutes or until a wooden pick inserted in center comes out clean. Cool cake completely in pan on a wire rack.
Place banana slices on top of cake. Top with Fluffy Cheesecake Frosting, and sprinkle with nutmeg. Cover and chill 8 hours.