Prepare cake mix as directed for cupcakes. Line cupcake tin with liners. Pour batter into each cupcake liner. Using a toothpick, drop a small amount of food coloring into the batter. Use a toothpick to swirl the coloring into the cupcake batter.
Bake as directed on box. While they cook, put a few drops of the same blue coloring into the tub of icing. Mix well. Let cupcakes cook when finished baking, then frost. Top each with a half of an oreo cookie to the cupcake resembles a shark fin.