Preheat oven to 350°F and grease two 8-inch cake pans.
Mix cake mix, water, oil, and eggs until smooth.
Gently fold in most mandarin oranges.
Divide batter between pans and bake for 23-27 minutes.
Cool cakes for 15 minutes, then transfer to a wire rack.
Mix pineapple, pudding mix, and Cool Whip for frosting.
Assemble cake with frosting between layers and on top.
Garnish with cherries and remaining oranges.
Chill for 4 hours before serving.