The Mermaid




An incredibly detailed custom mermaid costume with detachable shells, created for a company that does special appearances at kid's birthdays as princesses, pirates, & such. Little did I know that this would be the most involving project that I have ever undertaken!

When sketching up the design I had a few things to keep in mind for example how it had to be appropriate for children, very wearable, have an adjustable size, yet still beautiful & well made. The owner of this company approached me for a custom piece because of how most mass produced costumes are not durable enough to withstand a few seasons of parties, or in her budget.

The final product consisted of three major components:




Step 1: Bodice

The first step in designing this project was to keep functionality in mind, since my client is going to be around children most of the time, it needs to be age appropriate. Usually mermaid costumes consist of just wearing a shell bra, but we did not want much skin to show. To solve this problem I created the outfit as a strapless gown, with shells attached to the bodice.

To begin!

Outer bodice layer: Consisted of 7 pieces: center front, 2 side fronts, 2 side backs, 2 center backs with zipper allowance.  Used nude colored fabric making up the princess seamed bodice, and an eyelet corset panel inserted between the center back & side back pieces. These panels would be on the outside of the invisible zipper, making it possible for the wearer to cinch it smaller, or let it out according to who is wearing it once you lace it up. 

Boning: To add boning you simply leave 1" extra seam allowance to the inner layer pieces. This acts as the casing, and should be stitched shut once you are absolutely that you are happy with the length of each piece. For this I used a plastic style boning with a woven cover, sold by the yard at a craft store. Bought 1.75 just in case!

Bodice Lining: Made up of nude colored polyester lining fabric.  Since this is a mirror image of the outer layer, construct it the exact same way, but add 1" seam allowance for the boning casing. Also stitched padding to the breast area to add to the hourglass shape we were trying to achieve, you can use bathing suit pads or something similar for this.

Combine! At this point I basted the inside + outside together, made sure the seams matched, and stay stitched to finalize them. Turn right side out, press, and top stitch the top edge for structure. Go ahead and baste the zipper edges & bottom together for security.

Step 2: Shells

Since mermaids are always wandering around topless with some simple shells adorning their chest, this was the part I spent the most time fabricating from scratch. The shells had to be luminescent purple, with jewels that would really catch your eye!

Material: Have you ever heard of a magical material called Wonderflex? Well this stuff saved my life! It is used by costume designers, cosplay enthusiasts, and every one in between who need to make some type of wearable prop that is lightweight, yet very sturdy. It comes in big rolls and looks like a really heavy interfacing, with a fabric grid embedded in the plastic, and to use it you simply mold it with a  heat gun (or blow dryer in my case).  I had originally tried to make these shells out of clay, but that was a complete failure... until I used the clay molds as a cast for the wonderflex pieces.

To start that process I cut out two big circles from the material, about 11" in diameter. Placed this on top of the clay shell & started heating it with the blow dryer. After pushing, pulling, and molding the wonderflex to the correct shape, I let it cool & pulled it off the clay pieces, cut to the desired shape, and sanded those cut edges so that they would be smooth.

Note: since this material is heat set, DO NOT leave in a hot car or some other environment where the temperature can get warm. It will warp the form & not be good at all. 

Painting: Ended up doing about 4 layers of ombre purple paint until I got the desired look, and then covered it with a sparkle gloss which gave it a wet look. On top of this I super glued purple & white jewels. VOILA! This was such a tedious process, yet without the wonderflex, none of it would have been possible!

Later on I applied velcro sections to the insides of the shells, and the breasts of the bodice. This ensured that they could be removed for dry cleaning, and you wouldn't have to worry about them melting.

Check it out! This stuff is MAGICAL!

Step 3: The Tail

To create a tail that you could actually walk & sit in, I approached this as if it were a pencil skirt, very high waisted and tapered around the knee, yet with a large slit in the back at knee length. The skirt itself is made up of three very long pieces which when stitched together create a type of horn shape. This points towards the front, and leans to the right a bit so that the wearer can hold it up with a type of  wristlet on the right side.

Fabrics: Green polyester lining material, Fusiboo fusible batting for a structured inner layer, emerald foil lame on the outside, whith chiffon scales applied after the pieces have been sewn together. This makes 4 layers of fabric for the desired color, structure, and weight!

Scales: The scales were constructed using four yards of sparkle chiffon cut into 5" scalloped rows. This had to be the most time consuming part of the endeavor, since this was a woven material & it could not be fraying, I had to singe the edges of each row with a tea candle. The end effect was stunning, but wow did that take an eternity!

After singing all of the edges I combined the tiers of scales into a fabric of it's own, and there is another how-to I made on the subject found at:

Flipper: For this part I simply traced out a flipper shape from the Fusiboo& 8 layers of aqua organza, topstitched them together, and applied to the tail while inside out.

Step 4:

Putting all of the pieces together!

At this point I basted the bodice to the tail, but only to the outer tail layer, this let me blind stitch the tail lining to the bodice and give it a well finished look. I also added straps to the bodice side seam so that it could be hung up.

This was an intense project, but I am very proud knowing that kids in the Nashville area truly believe that my client is a sea princess! So awesome :)

You can find more of my work at:



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    13 Discussions

    Nicely done! I love how you made a full top instead of just a bikini top. It can get cold out and it's just nice not to show off a bunch of skin!

    1 reply

    Yes, and especially being around children, she did not want to worry about any wardrobe malfunctions. Thanks for reading!


    6 years ago on Step 2

    Nice work here, great pictures, informative and well written. Thanks from the staff at

    1 reply

    Reply 6 years ago on Introduction

    So glad my friend suggested this material, it really saved my life! Had no idea that this type of thing existed, and will definitely be using more in the future. Thank you for making something amazing!


    6 years ago on Introduction

    This is so precious! Great job !! I can't wait to show my son's girlfriend, she's been wanting to do a Cruella D'eVille or mermaid outfit....cant wait to start, Thanks!

    1 reply

    6 years ago on Introduction

    Very nice work and good Instructable'. I happen to have some large sea green and pearl sequins which I used on something similar and It occurred to me you might not mind my suggestion. ie. Add something "shimmery' just along, some not necessarily all, of the edges such as sequins, glass. pearl or silver. Even a glitter pen would work. This would catch the eye and enhance the underwater theme. Enjoy your costume. Regards.

    1 reply

    Reply 6 years ago on Introduction

    Thanks for the input! Unfortunately our schedule & budget did not allow for the extra scale detailing, which is why we had to choose a pre-sparkled fabric, yet in the future if I ever take this on again this idea will be used.