In a large bowl, beat the cake mix, water, eggs, and oil; beat on low speed for 30 seconds. Beat on medium for 2 minutes.
Pour into two greased and floured 9-in. round baking pans. Bake at 350° for 25-35 minutes or until a toothpick inserted near the center comes out clean. Cool for 10 minutes; remove from pans to wire racks to cool completely.
Using a serrated knife, level the top of each cake if necessary. Return layers, top side up, to two clean 9-in. round baking pans. Pierce cakes with a meat fork or wooden skewer at 1/2-in. intervals.
Drain juice from strawberries into a 2-cup measuring cup; refrigerate berries. Add water to juice to measure 2 cups; pour into a small saucepan. Bring to a boil; stir in gelatin until dissolved. Chill for 30 minutes.
Gently spoon over each cake layer. Chill for 2-3 hours.
Dip the bottom of one pan in warm water for 10 seconds. Invert the cake onto a serving platter. Top with reserved strawberries and 1 cup of whipped topping. Place the second cake layer overtopping.
Frost cake with remaining whipped topping. Chill for at least 1 hour. Serve with fresh berries if desired. Refrigerate leftovers.