Preheat oven to 350°F and line muffin cups with paper liners
Prepare cake batter according to package directions
Fill cups two-thirds full and bake until set
Cool cupcakes for 10 minutes in pan, then transfer to rack
Let cupcakes cool completely for about 30 minutes
Mix blue food coloring into frosting until evenly colored
Spread frosting over each cupcake evenly
Sprinkle crushed graham snacks on one side for sand effect
Cut fruit snack roll into strips and place on frosting
Add teddy grahams, gummy rings, and decorations on top
Finish with umbrellas and serve