I iced a 9×13 cake with butter cream icing and airbrushed one half blue then used the flat spatula to make “swirls” and have some white show for this Luau Birthday Cake. You can also spread some clear piping gel over it and lightly airbrush it blue. It gives it a more realistic water effect.
On the other side I airbrushed it brown then before it could dry I used a small flat spatula to swirl it so that it would look lighter in some areas and to give it texture, then lightly sprayed it yellow. I then took some yellow sanding sugar and sprinkled it over the sand. You can also just use brown sugar. I then used a #18 border tip on the top and bottom. I used a #6 for the “towel” but a #48 looks the best. I then “striped” a small piping bag with a small strip of green then filled the rest of the bag with a lime green for a two toned swirled effect, and used #233 to pipe some grass.
Then I used Luau pics that can be purchased from party supply stores for the rest.