HEAT oven to 350ºF.
COMBINE flour, dry gelatin mix and sugar in small bowl. Whisk in 1/2 cup water. Combine fruit in large bowl. Add flour mixture; toss to evenly coat.
SPOON into 10-inch cast-iron skillet sprayed with cooking spray.
MIX baking mix, sour cream and remaining water just until blended. Drop into 6 mounds over fruit mixture.
BAKE 35 min. or until fruit mixture is hot and bubbly, and biscuit topping is golden brown. Cool slightly before serving topped with COOL WHIP.