Blueberry Bottom Cake

Ingredients (9)

• + 1 (15.25 ounce) package white cake mix (such as Pillsbury® Classic White) add to pantry
• ✓ 1 cup water
• ✓ 3 eggs
• + ½ cup vegetable oil add to pantry
• ✓ 4 cups fresh blueberries
• + 1 cup white sugar add to pantry
• + 1 (3 ounce) package strawberry-flavored gelatin add to pantry
• + 3 cups miniature marshmallows add to pantry
• + 2 cups frozen whipped topping (such as Cool Whip®) add to pantry