Under the Sea Birthday Party
We threw an Under the Sea Birthday Party for my 3 year old, complete with a Mermaid Cake and Oyster Pearl Cookies. All of the food and decorations fit in with this beach ocean themed party.
For my youngest’s 3rd birthday, we hosted an outdoor Under the Sea Birthday Party. I’ll take you through the planning, decorations, food, and desserts. I’ve included lots of ideas for a fun and festive ocean themed party!
Mermaid Under the Sea Party
Because we were having an outdoor pool party for Charlotte’s 3rd Birthday, I encouraged her to choose a Mermaid Themed Party / Under the Sea Themed Party. She loved the idea!
I made her a shirt to wear on her actual birthday, which was a week before the party. Her shirt says “This little mermaid is 3.” I found some pretty holographic heat transfer vinyl at a local vinyl store and also a mermaid patterned vinyl that I used for the 3. I cut the vinyl using my Silhouette machine.
On her actual birthday, we took her out to lunch and to Build A Bear for their “pay your age” Bear. Because we got a good deal on the bear, we let her choose an outfit. You can see how nicely the bear matches her!
I also made my two older girls t-shirts to wear that day that say “Mermaid squad.” I designed them so the “A” in “Mermaid” is a starfish and the end of the “d” in squad has a mermaid tail. I used the same holographic vinyl as for Charlotte’s shirt.
Under the Sea Birthday Party Decorations
While Charlotte’s cake was Mermaid themed, I decided to go with an Under the Sea Birthday Party theme to give more options for decorating and fitting the food into the theme. I got so many of the ideas for this party from Pinterest. I will try my best to give credit to the source when possible!
DIY Fish Net Balloon Decoration
In designing the food table, the main focus was this fish net party decoration to hold balloons over the food table. It was a very windy day, which was quite frustrating when trying to assemble this focal point. Balloons kept blowing away and the lettering for “Charlotte is 3” kept blowing in all directions. It took more time than I had budgeted to get this assembled, but I have a few tips, as well as a suggestion I wish I had known about at the time.
I wanted pearlized balloons rather than typical matte ones to add some shine. In fitting with the color scheme, I chose white, purple, and seafoam colored balloons. We blew them up all around the same size. I’ve seen some where you blow some up large, some medium, and some small, which is also very cute.
To hang the fish net, I used clear fishing line to suspend the net from some nails under our deck. You could try using outdoor command hooks if you don’t already have an easy place to tie to the fishing net. I tied it up on each end and in the middle. Then, I folded the net up half way and started securing the sides together with clear fishing line. The spacing is important because you don’t want a balloon to be able to fit through and blow away.
Once a little pocket was created, I started tying up the top with fishing line to create a closed pocket, but I left enough space on one end to add the balloons. I added the balloons inside the net, then moved them over to fill it. Once full, I tied up the remaining section. At this point, it may be necessary to go back around all of the edges to make sure there’s not a hole for the balloons to escape. When the wind blows the net, it really puts pressure on the balloons and they can get out easily if the edges aren’t tied.
After this party, I attended a birthday party for my cousin’s son and discovered balloon garland strips. It’s a clear strip with little holes in it that is used to secure a bunch of balloons together for a balloon garland. This would have been much easier! If I had to do it over, I would first secure all the balloons to the strip, then place the garland into the net and then tie it in just a few places to secure the balloons. This would have prevented rogue balloons from escaping the net!
For the “Charlotte is 3” lettering, I cut individual letters of champagne glitter cardstock with my Silhouette machine. I then used a needle and fishing line (rather than thread) to poke through places on the cardstock so I could tie the letters to the fishing line. This was a bit tedious, but with the wind, it was necessary to secure each letter. Some of the letters could be tucked into the net.
I didn’t get a good picture of the “jellyfish” decorations I made. They were just mint / seafoam colored paper lanterns with strips of disposable table cloths cut up and tied onto the bottom of the lantern. Like I said, the wind was out of control, so these were blowing in the breeze, as you can see in front of Charlotte.
Under the Sea Centerpieces
As I’ve mentioned in my posts on Ava’s FROZEN Birthday Party and Cinderella Birthday Party, I like to use disposable tablecloths to decorate at parties. Not only are they a super inexpensive way to add color to the party, they make clean up so easy.
This table originally had a disposable table cloth on it, but the wind was blowing it up and knocking over the centerpieces, so we finally decided to ditch the table cloth. I used another fish net party decoration as a table runner and added some glass gems / glass vase fillers to weight it down.
I filled small metal flower pots from IKEA with tissue paper and glass gems and then stuck a wooden dowel rod in the center. The wooden dowels were covered in crepe paper and wrapped in jute twine. I then attached mermaid and seahorse silhouettes I cut out of glitter cardstock with my Silhouette.
To make this Mermaid “3” art, I used a circular craft punch to punch out purple, mint, and champagne glitter cardstock. I cut the “3” using my Silhouette and really pretty holographic, textured cardstock I found at a local craft store. I glued the circles onto a piece of 5×7-inch white cardstock to look like mermaid scales and then placed the 3 on top. I used an IKEA frame I already had that has a clear, plastic front instead of glass, as avoiding glass is ideal around a pool.
Nautical Rolled Napkins
Another Pinterest find! I purchased 3 colors of paper napkins and rolled them around plastic cutlery: a fork, a knife, and a spoon inside each napkin. I then tied them with jute twine in a fancy little knot and added a mint lifesaver candy. One tip about these candies: they are very minty. I recommend unwrapping them and letting them sit out for a few days before you need them to dampen the mint smell. I didn’t want the napkins to smell too much like mint.
During my many shopping trips while planning this party, I found this tumbler that matched the theme perfectly. This was a little gift to myself.
Ocean Themed Party Food
I wanted most of the food to fit the Under the Sea Party theme. I made the food labels with brown Kraft cardstock and a white paint pen. Adhesive rhinestones added a little bit of sparkle to the food labels.
We always serve snack by the pool to tide guests (and our kids!) over until dinner. The “seaweed dip” was Costco spinach artichoke dip, La Terra Fina brand. Tortilla chips and carrot stick “crab legs” were for dipping.
My kids are big fruit lovers, so no pool party would be complete without a fruit platter.
Lunch or Dinner
I kept it very simple and ordered a tray of Costco croissant sandwiches. They come as a variety of 3 sandwiches: ham and cheese, turkey and cheese, and roast beef and cheese. The tray also comes with a mustard mayo spread and a basil mayo spread. We’ve used these sandwich trays for birthdays and Baptisms when I’ve been too busy to make all of the food and desserts myself.
To make these “crab wiches,” I used hot glue to adhere googly eyes onto toothpicks. I assembled all of the googly eye toothpicks in advance and then placed them into the sandwiches to look like crabs before serving the sandwiches.
When she turned 3, Charlotte was super picky. She was even in occupational therapy for eating issues! I knew she wouldn’t even try one of the croissant sandwiches. One of her favorite foods at the time was Uncrustables, and because of the shape and crimped edges, I called these “clam wiches.”
We had salad with homemade croutons and chips, but none of these had themed labels.
These dill pickles were “sea cucumbers.”
These green grapes on wooden kabob skewers were labeled “seaweed.”
We made multiple boxes of Velveeta Shells n Cheese and labeled them “shells & cheese.”
This jello was another Pinterest find. It’s called “sea glass” (or “beach glass”) and has different layers.
It’s basically just blue and purple jello, each divided into two portions. One was left plain and the other has whipped topping (Cool Whip) folded in to make it opaque. The jello was then all layered into disposable clear cocktail cups so each guest could just grab one from the buffet.
See all of the layers!
I saw this idea on Pinterest and thought they were SO cute, I just had to make them. We didn’t really need another dessert to go with the Mermaid Ice Cream Cake, but I usually like to offer an alternative.
These cookies are easy for guests to grab, just like a Bar dessert, so they can be offered as a sweet treat before the main birthday cake is served. All the details for making the cookies are in the post Oyster Pearl Cookies.
I did not serve these at the party, but these painted Starfish Cookies would have been super cute with this theme!
My girls are big fans of my Dairy Queen Copycat Homemade Ice Cream Cakes. One of my favorite things about ice cream cakes, aside from the fact that they taste AMAZING, is that the top is a literal blank canvas for decorating.
Charlotte really wanted an ice cream cake, so I decided to decorate the top to fit the theme of Mermaids and Under the Sea. All the details of how to decorate the cake and make the ocean themed fondant decorations are in my Mermaid Birthday Ice Cream Cake post.
Our Little Mermaid certainly had a great birthday!
Summary of Under the Sea Birthday Party Sources
I purchased many of my supplies locally but will list some online sources as well for convenience.
Fish net party decoration
Clear fishing line
Balloon Garland Strips (I did not use but wish I would have!)
Glass gems vase filler
Circular craft punch
Brown Kraft cardstock
White paint pen
Googly eyes and toothpicks
Hot glue gun
Disposable table cloths
Under the Sea Dessert Recipes
Looking for More Birthday Party Ideas?
Check out these other Parties I’ve thrown for my girls:
Daniel Tiger Birthday Cake and Party
Very Hungry Caterpillar Birthday Party
Sesame Street Birthday Party
My Little Pony Rainbow Unicorn Ice Cream Cake
FROZEN Birthday Cake and Party
Cinderella Birthday Cake and Party
Tea Party Ideas for Kids
Penelope Bird Birthday Party
Winter Wonderland Birthday Party
These Rainbow Brownie Ice Cream Sandwiches and Painted Rainbow Cookies were just for fun but would be perfect for a Rainbow Birthday Party!