In advance: Make sea plants and sea urchins. Prepare Royal Icing recipe. Using combination Leaf Green/Lemon Yellow royal icing, pipe Leaf Decorating Tip 352 ruffle sea plants on waxed paper covered board. Using combination Rose/Violet royal icing, pipe Multi-Opening Decorating Tip 233 pull-out sea urchins on waxed paper covered board. Make 1 plant and urchin for each cupcake and let dry. Make cookie fish. Prepare Roll Out Cookie Dough recipe and roll ¼ in. thick. Use smallest round cutter from 101 Cookie Cutters Set to cut bodies. Thin dough with water to a piping consistency. Place dough in bag fitted with Round Tip 3 and use to pipe mouth, fins and tail. Bake for 7 to 8 minutes at 350°F. Let cool. Using white royal icing, pipe Round Tip 3 ball whites of eyes. Using black royal icing, pipe Round Decorating Tip 2 dot pupils.
Bake and cool cupcakes in White Standard Baking Cups, and cool completely on Cooling Grid.
Prepare Buttercream Icing recipe. Tint the icing using a small amount of Royal Blue Icing Color. Use spatula to ice tops of cupcakes with blue buttercream icing.
Position iced cupcakes on stand. Insert fish cookies, sea plant and sea urchin.
Why not change the color of your fish, sea plants and urchins? You can even add starfish and sea horses with tip 3 and royal icing.