My Under the Sea Cake DIY

My Under the Sea Cake DIY

We spent a week in Grand Cayman doing lots of snorkeling before my daughter’s 7th birthday, so when I asked her what theme she would like for her party, she choose Under the Sea.

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The finished Under the Sea themed birthday cake decorated with fondant sea creatures, pearls for bubbles, and graham cracker sand.

I’ve mentioned before that I’m a pretty good baker, but I’m not very a good at decorating cakes. I still love to make my daughters birthday cakes though, so I’m always looking for ways to make the cake look decent without strong decorating skills. I found these Cute Under the Sea Silicon molds and decided to attempt homemade fondant for the first time.

I used a Marshmallow Fondant recipe from The Spruce Eats that can be found here. It was very quick and easy to make, and once it was mixed up, I just split the fondant into 4 bags and dyed each bag a different color. I used orange, green, pink and purple. Once my fondant was colored, I just pressed a small amount into the silicon molds, and then pressed on the back of the molds to release. I let my fondant dry on parchment paper overnight.

Once my fondant decorations were ready to use, I baked my cakes (I made 3 8 inch cakes for the top tier and 3 10 inch cakes for the bottom tier), made a batch of buttercream frosting, stacked my cakes, and pressed the fondant decorations to the buttercream. You can find my favorite cake and buttercream recipes, along with my stacking technique on my Hula Girl Cake Blog Post.

The fondant was really easy to make and the molds made the fondant decorations look like they were made by a cake decorator and not a preschooler playing with play dough (which is how they would have looked if I made them by hand).

Close-up of the Under the Sea cake showing fondant sea creature decorations pressed onto the buttercream frosting.

I didn’t smooth out the buttercream before adding the fondant decorations because I thought it would look more like water, after putting the fondant on I decided I would have liked it better smooth, but didn’t want to risk damaging the decorations, so I left it more natural. Thankfully my daughter didn’t mind the rough look and was happy with her cake!

To finish off the cake decorations, I added a few white pearls for bubbles and sprinkled graham cracker crumbs for sand along the bottom cake board.

I decided to make extra use of the silicon molds and also used them to make some white chocolate shells and tails to include on the party favor table. I just melted some white chocolate melting wafers, poured it into the molds, tapped the molds a few times to remove air bubbles and placed the mold in the refrigerator for 10-15 mins. Once I had enough made, I added some graham cracker crumbs to sandwich bags, added a few shells and tied the bags closed with ribbon!

White chocolate shell and tail candy party favors in bags with graham cracker sand, tied with ribbon.

MagpieTayleetot is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com. All items used in this tutorial were purchased by me and I did not receive anything in exchange for this post.

Profile Image Miranda Weldon

Miranda Weldon

Miranda Weldon is the owner and Chief Crafter at MagpieTayleetot. An accountant by trade, who left the world of finance in pursuit of more creative ventures. This mother of two and Class "Room Mom" to many, loves to DIY snacks, party supplies, and more! Miranda is a self-taught seamstress of 15 years who always prefers to make things herself.

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