HomeDIY CraftUnder The Sea Birthday Party

Under The Sea Birthday Party

Under the sea birthday party ideas

Throw a fun and magical birthday party under the sea! If your kids are obsessed with all things ocean and water, you know that there are many different types of topics to choose from. Here you’ll find ideas suitable for mermaids, sharks, or a general ocean/undersea theme.

Planning a kid’s birthday party can be a little stressful, but it doesn’t have to be! These decoration ideas, crafts, activities, sea themed treats and party favor bags are super easy to make a day or two in advance so you don’t have to spend a lot of time planning.

Under the sea party decor

A woman sets up a water-inspired balloon wall.

Water inspired balloon wall

Balloon walls are one of the simplest ways to decorate a party. Stick different shades of blue balloons to the wall using masking tape. Mix in a few small clear balloons so they look like bubbles in the water!

Image source and inspiration by Oh happy day

Purple decoration and disco ball

DIY Mylar Party Banners

The colors used in this mylar party decor can be completely changed to fit your party theme. Mermaids, sharks, or ocean themes that use pastels, greens, and yellows can all be amazing uses for this type of decoration. All you have to do is cut and secure strips of mylar paper for a secure fence, that’s it!

Image by DIY Studio

Seaweed hanging on the wall.

Seaweed signage idea

Create these seagrass strips by rolling and securing green crepe tissue paper to the wall. It’s so simple but helps bring this ocean theme to life!

Image source and inspiration by Shakira events

Sea themed banner decor.

Shark themed party idea

Colorful Mylar tissues can be hung on the ceiling or wall, and can also be used as photo backdrops.

Image source and inspiration by 100 layer cake

Undersea games and activities

Beach print art.

Beach print art

Grab a piece of butcher paper or white poster board and create a beach scene and then have the kids draw their feet and step on the board to create footprints. This craft is super simple and fun for all kids, especially toddlers and preschoolers!

Image source and inspiration by Hi cool

Artistic image of a sand paper castle on a table.

Sandcastles from sandpaper

If you have some sandpaper, use it to make these adorable sandpaper sand castles. This craft project is the perfect ocean-themed activity. Cut sandpaper into a sandcastle shape and then decorate with seashells, glitter, glitter glue, or sequins. I would choose a lower grit sandpaper for this craft so it won’t be as rough on your kids’ fingers!

Image source and inspiration by Mama’s diary

Rainbow foam bubbles swirled by a child.

Rainbow soap bubbles

Most kids are obsessed with water and bubbles, and this rainbow soap suds bubble activity can be really fun for sensory play or as a party activity for everyone. Add food coloring to your soap mixture to create different colors of bubbles and then add everything to your bathtub or kids pool outside.

Image source and inspiration by Fun at home with kids

Ideas for ocean themed foods and desserts

Sandcastle cake on a stand on the table.

How to make a sandcastle cake

Any ocean or under the sea themed birthday party *needs* a sand cake. This adorable cake actually looks like a sandcastle from the beach. Cover your favorite cake with buttercream. Crushed vanilla wafers make “sand” shells and marshmallows are really cute decorations!

Image source and inspiration by Beautiful mess

Ocean cake on a plate.

Ocean cake

This ocean cake is easy enough for anyone to make and is sure to be perfect for your little one’s ocean-themed birthday party. Bake your child’s favorite cake, and mix the buttercream with food coloring to create different shades of ocean blue. The tubular green frosting is used to make seaweed and crushed graham crumbs for sand.

Image source and inspiration by Childhood magic

Madeleine, which resembles an oyster

Pink shell madeleine

If you’re having a mermaid-themed birthday party, these pink-crusted madeleines are a delicious dessert to serve! Decorate store-bought or homemade madeleines with pink or purple edible spray. Attach the two shells together with more frosting and finish with sugar beads or mini gum balls in the middle.

Image by DIY Studio

Top photo of graham cracker snacks on the table.

Ocean Graham Cracker Snacks

Ocean graham cracker snacks can be something delicious to serve during a party or can serve as a fun kid-friendly activity. Everyone can have fun decorating graham crackers with blue frosting, crushed graham crackers, sprinkles, white sugar pearls for bubbles, and goldfish.

Image source and inspiration by Cutevitity

Under the seafood table.

Crab dip

Cut up red peppers to make them look like crabs! Add toothpicks with googly eyes on top to finish it off. For the actual dip, you can serve whatever you want, real crab sauce, ranch, or whatever your kids enjoy.

Image source and inspiration by It almost makes perfect

Blue lemonade popsicles stacked on a plate.

Ocean blue lemonade popsicles

Cool down with an ocean blue lemonade popsicle! Your kids will love this themed dessert, it looks like fish are swimming in the ocean. Place the shark or swede into popsicle molds, then add blue food coloring to the store-bought or homemade lemonade to drizzle over.

Image source and inspiration by Play party plan

Under the sea party favors

Shell soap

DIY chocolate inspired by 80s soap

These handmade chocolates are inspired by your grandmother’s shell soap from the 80s! These antique-looking chocolates are easy to make using pastel-colored candy melts and some shell molds. Chocolate is always the perfect gift, and these chocolate shells fit into any ocean-themed party bag!

Image by DIY Studio

Under the sea party favors hanging on string.

Under the sea party favors

These ocean creature party favor bags are simple and no-fuss to put together. Add M&Ms or your favorite candy mix to the middle of several sheets of tissue paper (so nothing falls out) and then attach them to look like an octopus!

Image source and inspiration by Leah Griffith

Fish party favor bag on a table full of candy.

Fish Party Favor Bag + Free Printable

These under the sea party favor bags look like little fish! Using the printable from Oh Happy Day, fill cello bags with colorful candy and then secure the bottom with washi tape to create these adorable little fish party bags!

Image source and inspiration by Oh happy day

More party ideas

Under the Sea is a fun party theme. You don’t need to spend a lot of time planning or preparing to throw a great party for your kids and create great memories with your family!


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