Preheat the oven to 350℉. Spray a 13x9-inch pan with nonstick spray.
In a large bowl, use an electric mixer to combine the cake mix, oats and butter until crumbly. Press 3 cups of the crumb mixture into the bottom of the prepared pan. Bake for 10 minutes. Cool the pan on a wire rack for 5 minutes.
In a small bowl, stir the jam and water until blended. Spread it over the crust. Sprinkle with the remaining crumb mixture. Bake for about 25 minutes, or until lightly browned. Cool completely on a wire rack. Cut into 24 bars.