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170+ Splashy DIY Under the Sea Halloween Costumes

The deep blue waters conceal the hidden depths of the marine life lurking there. Your under the sea costumes are just a dive away in this cool DIY collection.

Learn how others have made octopuses, glowing jellyfish and even a seahorse. There is no limit to the underwater creatures you can create. When you see how people here have constructed their homemade costumes, you will be inspired to take on your own subaquatic ensemble.

One popular option is, of course, mermaid costumes. The most famous being The Little Mermaid, but plenty of other original mermaids are flicking their tails here.

Another sea creature not associated with reality, you will be glad to encounter Sharknado costumes here. Every bit of detail brings these costumes to another level of hilarity.

In addition, check out this clever idea of bringing the water to you with an aquarium costume. There are incredible instructions here where you can learn how to make them glow.

So take the plunge this Halloween and dive into one of the awesome oceanic inspired homemade costumes here!

Latest Under the Sea Halloween Costumes

2023 Homemade Costume Contest

Featured Under the Sea Halloween Costumes

Life Aquatic Family with Jacques Cousteau Baby Scuba, Ocean Mom and Giant Squid Dad

Life Aquatic Family with Jacques Cousteau Baby Scuba, Ocean Mom and Giant Squid Dad

I’m not sure where this trait came from, but I am a bit obsessed with costumes. I will spend time that I don’t have to hand craft extravagant costumes that will be worn for an hour or so. Why? I’m not sure. I just can’t seem to help myself. Being that this is Archie’s first Halloween, I decided it should be a good one. I love all things Wes Anderson, Life Aquatic, The Beatles Yellow Submarine and of course, Jacques Cousteau. It seemed only appropriate that “Adventure Baby” (our nickname for Archie) be dressed as a mini scuba diver. Read more »

Stunning Homemade Jellyfish Costume

My daughter and I were watching Finding Nemo and as soon as she saw the part that Dory and Nemo jump on the tops of the jellyfish, she decided she wanted to be a jellyfish for Halloween.  She wanted to use a clear umbrella as the base but we decided that a hat style might be easier for her to wear while trick or treating. The base of the jellyfish is a sombrero.  I filled the brim with newspaper and bubble wrap so it would still be fairly lightweight and covered it with a piece of scrap fabric I had. Read more »