My daughters both wanted a castle cake, but I made them one a year earlier. So, I decided to take the Wilton Castle Cake kit and repurpose it.
I decided to make the castle into a sand castle on the water. It was very simple to make.
The first thing I did was prepare the towers. I took the plastic towers from the kit (you can also use regular ice cream cones with waffle cones on top) and coated them with a thin layer of icing and rolled them in crushed graham crackers. I let those dry over night. Next, I made a six inch round cake and one 12x18 inch cakes. I iced the sheet cake, then I iced the round cake on a separate plate and coated that with the graham crackers. Then, I placed the round cake in the corner of the sheet cake. I made more "sand" around the round cake.
I piped on a border to the cake.
The next step was the "water". I had no idea how to do water at first. I always heard about people using Jell-o. I didn't want to get that messy, so I chose to use Piping Gel, which you can find at any craft store (10oz tub). I tinted the gel teal and spread it over the cake making waves with my spatula.
The next thing to do was insert the towers in the cake. Just make sure they are pushed into the cake good enough or they will fall. You can also use dowels to secure them. I then put on the windows (if you don't have the kit, use the waffle pretzels).
The last thing I did was add the shells to the bottom border of the cake. I did make the shells ahead of time using a shell candy mold and mint chocolate (the kids loved it). I simply iced a swirl around the bottom of the cake and added the shells.
It sounds like a long process, but I don't think it took too much time as long as you prepare ahead of time.