Whether you are on an island or in the city, an ocean themed cake can make you feel like you're in the warm sun enjoying the soft sand of the beach. When creating a cake with an ocean or beach theme, it is important to make the pieces look as realistic as possible. Try referencing pictures of real seashells, beach balls, etc., while making your decorations for a more realistic look.
It can be difficult to make frosting resemble sand for a beach themed cake. Rather than trying to make your buttercream look like sand, coat the cake with a layer of buttercream and then use edible sand composed of brown sugar and crushed graham cracker. Use a food processor to finely grate graham cracker pieces and mix them with equal parts of brown sugar. Sprinkle the mixture over a freshly frosted cake so it will stick.
Seashells can be difficult and time-consuming to sculpt out of fondant or gumpaste. To save time, you can make seashells by pressing them into chocolate candy moulds using pre-made fondant. Knead your fondant until it is smooth and pliable. Press a small ball of fondant into a chocolate seashell candy mould. Turn the mould over and remove the fondant sea shell. After it has dried, dust it with gold, pink, blue and white lustre dust to leave a shiny finish. Lustre dust, or pearl dust, is an edible food powder available in craft stores that is applied to food products using a brush. Apply lustre dust by using a small amount on the bristles of a craft brush and dusting it onto the surface of the food item.
Coral is a complex piece from the ocean that can be replicated for an ocean-themed cake. Rather than trying to sculpt a piece of coral by hand from gumpaste, you can create a piece of coral using leftover grape stems, royal icing and a little icing colour. Royal icing is a stiff, white icing that can dry hard and is made from meringue powder, water and icing sugar. Royal icing is not meant to be used for frosting cakes or cupcakes, due to the stiffness of the icing itself. Dye royal icing to the colour you want. Use a piping bag to cover a piece of grape stem with a layer of royal icing, and allow it to dry. Repeat this process on the same stem until it is completely covered.
The ocean moves and flows smoothly. Though you can use buttercream to create the appearance of the sea, it will not look as smooth or clear as real water. Instead, frost your cake with a thin layer of light green buttercream. Take clear piping gel and add in a few drops of blue. Apply the piping gel where you want water on your cake. Use an "S" pattern to create choppy ocean waves. With your cake spatula, pull the piping gel up quickly next to the seashore to create the look of waves crashing on the sand.