first birthday girl theme, under the sea theme birthday party

The sweetest first birthday girl theme: ONEder the Sea!

Life, Motherhood

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Looking for the cutest first birthday girl theme? Check out our ONEder the Sea party ideas! Our daughter Sage loved her mermaid-themed party, and we’re excited to share all the details with you. From invitations to party favors, here’s how we celebrated her first year of life!

We are coming up on Sage’s SECOND birthday in a few weeks! I can not even believe it. I swear her first birthday was just last month. And now I’m sending out invitations and buying decorations for her second birthday. Time is such a thief!

It has me reminiscing on how much fun planning and celebrating her first was. We had just moved into our new house, and only a few weeks later hosted all of our family and close friends to celebrate our girl’s first birthday party! 

There are so many adorable, creative first birthday girl themes out there, for her’s we went with: ONEder the Sea! She loved her mermaid dolly, and thankfully I had kept a bunch of cute decorations and seashell plates from when I had my mermaid-themed bridal shower. So it was the perfect fit! And I sort of went all out! But you gotta, because you only turn one once, right?!

first birthday decorations

  • We bought this adorable editable Oneder the Sea Mermaid Birthday Invitation from Etsy.
  • I got a lot of the party decorations from Amazon including seashell plates and bowls, jellyfish paper lanterns, mermaid tail balloons, tablecloths, mermaid garland, and more
    • *TIP: save all of the packaging in case you don’t use something, so then you can return it! 
  • The cutest mermaid birthday banner from Etsy
  • I found a bunch of the bowls and large platters from HomeGoods, I linked similar ones in this Amazon ‘first birthday party’ list too! 
  • I found the cute ocean-themed beaded pillows at HomeGoods. We’ll use them for future summer decor! 
  • Our family friend put together her balloon mermaid tail, I purchased the balloon set from amazon! 
  • For the flower center pieces I just went to our local grocery store and grabbed a bunch. They have stunning, affordable bouquets! And I put them together myself with vases we already had. 
  • For the table runners I went to JoAnn Fabrics and grabbed a couple pieces on sale! 
  • Then we just put out pictures of our girl, and put her cake smash picture up on our Samsung FrameTV!

first birthday cake

I was OBSESSED with her under the sea cake! I got the inspo from pinterest pictures, sent them over to the bakery and she absolutely captured the theme perfectly. We ordered from Sweet Solutions in Canandaigua, NY. We also had beautiful under the sea cookies made!

first birthday party outfit

My mom found this adorable rainbow tulle dress from! As of writing this, it is still available!

And I bought her this beautiful mermaid themed ‘one’ crown on Etsy.

first birthday party food

To go along with the under the sea theme, we had fun pick-me-ups like ‘fish’ aka goldfish and swedish fish, ‘driftwood’ aka pretzel sticks, ‘oysters’ aka oyster crackers, and lots of others! Our main dishes were sushi (obvi) + subs!

first birthday party favors

We found cute and affordable sand toy sets at TJMaxx! 

If I missed anything, feel free to ask in the comments! And let me know if you plan on doing this first birthday party girl theme for your little one.

Alright, now I’m all in my mama feels and am going to go sob soaking up the last few weeks before my baby turns TWO!!!

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