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Successfully sewing a swimsuit depends on more than choosing the right fabric. You also need swim notions that can withstand chlorine, saltwater, sunlight, and repeated wear. These include polyester thread, swimwear elastic, stretch needles, clips, rings and sliders, hooks, and swim clasps.
In this guide, you’ll learn which swimwear notions are essential, what each one does, and how to choose options that work with your fabric and pattern. We’ll also cover the best stitches and tools for sewing swimwear, how to match lining and elastic to your main fabric, and which common mistakes can affect fit and durability.
It’s easy to focus on the exciting parts: the colour, print, or swimsuit style, and treat the smaller supplies as an afterthought. But those little components do a lot of the heavy lifting. The right elastic keeps openings secure, the right needle prevents skipped stitches, and water-safe hardware helps your finished swimsuit hold up beyond its first trip to the pool.
Whether you’re sewing your first bikini or adding another handmade suit to your collection, choosing compatible notions will help the project feel more manageable and give you a finish that’s comfortable, supportive, and made for real movement.
Swim sewing notions are the specialised tools, hardware, elastics, and supplies used to make durable swimwear. They're designed to work with highly stretchy fabrics while withstanding repeated exposure to chlorine, saltwater, sunlight, and constant movement.
If you've sewn garments before, you'll already be familiar with general sewing notions like pins, thread, scissors, and needles. While many of these tools still have a place in your sewing room, swimwear requires additional ones.
Here are some of the reasons why sewing swimwear requires different notions:
Standard elastic often loses its stretch after repeated swimming.
Cotton thread can deteriorate surprisingly quickly when exposed to chlorine.
Universal needles work well for wovens and lower-stretch knits, but once you move into high-spandex swim fabrics, they're more prone to skipped stitches. That's because a universal needle isn't shaped to slide between the tightly packed fibres of a stretch knit the way a dedicated stretch needle is.
Decorative hardware may rust after only a few trips to the beach.
Specialised swimwear notions are designed to solve these problems before they happen.
The good news is that you don't need an enormous collection of supplies to sew beautiful swimwear. A carefully chosen set of quality notions will make construction easier, improve the durability of your garments, and help your projects look far more professional.
Think of them as an investment in every bathing suit you'll make and not just the one currently on your cutting table.
Swimwear stretches, gets wet, and is exposed to chlorine, salt water, and sunlight, so every component needs to work together.
Because most patterns use negative ease, the swimwear fabrics, elastic, thread, and lining must all stretch and recover properly. Purpose-made notions help prevent loose openings, broken seams, and fabric damage while making the sewing process easier to manage.
You don't need an industrial workshop to sew professional-looking swimwear, but having the right tools makes the entire process smoother and more accurate.
Let's look at the essentials.
Sliders and Ring
Sliders and rings are usually used together to create adjustable swimsuit straps. The ring connects the strap to the garment, while the slider lets you change the strap length for a more comfortable fit.
They’re commonly used on:
Bikini tops
camisoles
Bras + bralettes
slips
lingerie
activewear
Choose hardware that matches the width of your strap or elastic. If the ring or slider is too large, the strap may shift. If it’s too small, threading and sewing can become unnecessarily fiddly.
For swimwear, use smooth plastic or coated metal hardware that can withstand chlorine and salt water without rusting, discolouring, or damaging the fabric.
S-type closure hooks are used to fasten bikini tops, swimwear bands, and other garments that need a secure, low-profile closure. Their curved shape slides neatly into a fabric loop while keeping the finish clean and comfortable.
Fabric + Flow offers S-type closure hooks in 20 mm and 25 mm sizes, with gold, black, silver, and white colour options to coordinate with your fabric and other hardware.
Choose a hook size that matches the width of your finished band. A closure that’s too narrow can bunch the fabric, while one that’s too wide may shift or feel bulky.
Swim clasps are another common option for bikini back closures, offering a secure, low-profile alternative to S-hooks.
Fabric + Flow carries swim clasps in two widths, 20 mm and 25 mm, so you can match the clasp to your back band rather than forcing a fit. A clasp that's too narrow can pull or pucker the band, while one that's too wide may sit loosely and shift during wear.
Choosing the correct width up front saves a fiddly adjustment later, especially if you're making the back band from the same fabric as the rest of the suit.
One of the biggest surprises for many sewists is how little pinning is involved when making swimwear.
While pins work well for many woven fabrics, they can leave visible holes in high-spandex knits and may even snag delicate fibres. So, swimwear makers always reach for fabric clips.
Fabric clips:
hold slippery fabric securely
don't puncture the material
prevent accidental snags
are easy to reposition while sewing
work especially well with multiple layers of fabric and lining
They're particularly helpful when working with swimwear lining, elastic, and folded edges where several stretchy layers need to stay aligned.
You'll probably still use pins occasionally, but clips are generally the safer choice for modern swim fabrics.
Read our complete guide to find out when to use pins and when to use clips.
The needle you choose has a surprisingly big impact on stitch quality.
For swimwear, stretch needles are strongly recommended because they're designed to slide between the knit fibres rather than piercing them.
This reduces:
skipped stitches
fabric damage
runs
visible holes
For dense nylon-spandex swim fabrics, a stretch needle is usually the best choice.
Dedicated stretch needles also feature a specially designed scarf behind the needle eye that helps prevent skipped stitches when sewing highly elastic fabrics.
If you've ever sewn a seam only to discover random gaps in the stitching afterwards, the needle, not the machine, is often responsible.
Learn more from our complete guide to stretch needles.
The best thread for sewing swimwear is 100% polyester thread. Polyester resists chlorine, salt water, sunlight, and repeated stretching far better than cotton thread, helping your swimsuit last longer and maintain strong, reliable seams.
When you're choosing swim sewing notions, thread might not seem like the most exciting purchase, but it's one of the most important. Even if you've invested in premium swimwear fabrics, quality swimwear elastic, and a well-drafted pattern, using the wrong thread can shorten the life of your garment.
Swimwear is exposed to conditions that most everyday clothing never experiences. Chlorinated pools, salt water, sunscreen, UV rays, and constant stretching all put stress on every seam.
100% polyester thread is designed to handle these conditions because it:
resists chlorine damage
won't weaken as quickly in salt water
stands up to repeated stretching
has excellent abrasion resistance
performs well in sunlight
creates durable seams that move with the fabric
Good-quality polyester thread also feeds smoothly through most domestic sewing machines and sergers, making it a reliable choice whether you're sewing your first bikini or your tenth one-piece.
Cotton thread works beautifully for many sewing projects, but swimwear isn't one of them.
Natural cotton fibres gradually weaken when they're repeatedly exposed to moisture, chlorine, and UV light. Over time, seams sewn with cotton thread can lose strength even if the surrounding fabric still looks perfectly fine.
It's one of those mistakes that's easy to make because the swimsuit may look beautiful, but the problems usually don't appear until after several swims.
For swimwear, polyester simply offers the durability these garments need.
Most swimsuit fabrics are made from blends of nylon and spandex (also known as Lycra or elastane). These fabrics stretch repeatedly while maintaining their shape, so the thread needs to keep up.
A high-quality polyester thread complements these fabrics by providing strength without becoming the weak point in the seam.
If you're shopping for supplies, it's worth buying thread from a reputable manufacturer rather than choosing the cheapest option available. A few extra dollars spent on quality thread can make a noticeable difference to the garment.
Swimwear elastic is specially designed to retain its stretch after repeated exposure to chlorinated and salt water. Unlike ordinary elastic, it helps your swimsuit maintain its fit, support, and shape over time.
When people think about sewing swimwear, they often focus on the fabric. In reality, the elastic does just as much work.
It creates the snug fit around leg openings, necklines, waistbands, and underbust bands while allowing the garment to stretch comfortably with your body.
Without quality elastic, even beautiful swimwear fabrics can quickly lose its shape.
Standard elastic simply isn't designed for life in the pool or ocean.
Swimwear elastic is manufactured to resist:
chlorinated water
salt water
repeated stretching
body oils
sunscreen
heat and sunlight
This helps your swimsuit recover its original shape after every wear rather than gradually becoming loose and baggy.
You'll often come across both cotton-covered and rubber-based swimwear elastics.
Many sewists enjoy working with cotton-covered swimwear elastic because it's easier to handle under the sewing machine. The woven cotton exterior provides a little extra grip, making it less likely to twist while being sewn into curved seams.
Rubber elastic can also work well but sometimes feels a little more slippery during construction.
The important point is choosing elastic that's specifically labelled for swimwear rather than general garment sewing.
Applying elastic isn't just about stitching it into the seam.
It also needs to be sewn under controlled tension so the swimsuit hugs the body comfortably without feeling restrictive.
Stretching the elastic too much creates tight, uncomfortable openings.
Not stretching it enough allows the swimsuit to gape.
Most commercial and independent swimwear patterns include guidance for how much tension to apply in each area, so it's worth following those instructions rather than guessing.
A three-step zigzag stitch is widely considered the best choice for attaching swimwear elastic.
Unlike a regular zigzag, the three-step version creates multiple smaller stitches that distribute stress more evenly across the seam.
The result is:
greater durability
improved stretch
stronger seam recovery
reduced thread breakage
If your machine doesn't offer a three-step zigzag, a wide, short zigzag stitch is an excellent alternative for domestic machines.
Foam cups are optional swim sewing notions that provide shaping, modesty, and light support. They aren't essential for every swimsuit, but they can improve comfort and confidence depending on the style you're making.
Many beginner sewists assume every swimsuit needs foam cups. In reality, plenty of modern swimwear relies on fabric, lining, and elastic alone for support.
Whether you use cups depends on the pattern, your personal preference, and the amount of shaping you want.
Using a straight stitch: Choose a three-step zigzag, wide short zigzag, or serger stitch so the seams can stretch.
Using the wrong needle: A stretch needle helps prevent skipped stitches and fabric damage.
Pinning delicate swim fabric: Use fabric clips to avoid snags and visible holes.
Stretching the fabric while sewing: Let the machine feed the fabric and use a walking foot if the layers shift.
Using regular elastic: Swimwear elastic is designed to withstand chlorine, salt water, and repeated wear.
Applying too much elastic tension: Follow the pattern measurements and distribute the elastic evenly.
Choosing fabric with poor recovery: Test a scrap to make sure it returns to its original shape after stretching.
Using non-swim hardware: Rings, sliders, and hooks should be smooth, water-safe, and the correct width for the straps.
Most swimsuit projects require stretch needles, polyester thread, swimwear elastic, fabric clips, and the notions specified by your pattern. Depending on the design, you may also need rings and sliders, S-type closure hooks, swim clasps, or foam cups.
Sliders and rings create adjustable straps on bikini tops, one-piece swimsuits, activewear, and lingerie. The ring connects the strap to the garment, while the slider lets you adjust the strap length for a more comfortable fit.
Choose hardware that matches the finished width of your strap or elastic. Hardware that's too small can be difficult to thread, while hardware that's too large may allow the strap to shift during wear.
Both are used to fasten bikini tops and swimwear bands.
S-type closure hooks slide into a fabric loop and create a lightweight, low-profile closure.
Swim clasps are two-piece closures that click securely together and offer a clean, professional finish.
The best choice depends on your pattern and personal preference.
It's best to use hardware specifically designed for swimwear. Swim-safe rings, sliders, hooks, and clasps are made to withstand chlorine and salt water without rusting or damaging your fabric.
Use 100% polyester thread. It resists chlorine, salt water, sunlight, and repeated stretching much better than cotton thread, making it the most durable choice for swimwear.
Choose elastic that's specifically labelled for swimwear. It's designed to retain its stretch after repeated exposure to chlorine and salt water and provides better recovery than standard garment elastic.
Yes. Stretch needles are recommended because they're designed for highly elastic knit fabrics and help prevent skipped stitches and fabric damage.
Fabric clips are usually the better choice. They hold slippery layers securely without leaving holes or snagging delicate swim fabrics.
No. Many one-piece swimsuits don't use closures at all. However, bikini tops with back bands often require either an S-type closure hook or a swim clasp, depending on the pattern.
Choose hardware based on its job. Sliders and rings create adjustable straps, while S-type closure hooks and swim clasps secure bikini backs and swimwear bands.
Match hardware to the finished strap or band width. Rings, sliders, hooks, and clasps that are too large or too small can shift, bunch the fabric, or make construction more difficult.
Use swim-safe materials. Hardware should withstand chlorine, salt water, and repeated wear without rusting, discolouring, or damaging the fabric.
Support the hardware with the right sewing supplies. Polyester thread, swimwear elastic, and stretch needles help the rest of the swimsuit stretch, recover, and hold up over time.
Use clips and stretch-friendly stitches. Fabric clips protect delicate swim fabric, while a three-step zigzag or wide, short zigzag allows seams to move with the garment.
Check the pattern before buying notions. Confirm the required strap width, back-band width, elastic, and closure style so every component works together.
Before you start cutting, check your pattern for the exact strap width, back-band width, elastic, and closure style it requires. That makes it much easier to choose sliders and rings, S-type closure hooks, or swim clasps that fit properly and work with the rest of the design.
A little planning here can save you from bunching, shifting hardware, or last-minute adjustments later. Once your fabric, elastic, thread, needles, and hardware are all compatible, the sewing process feels much smoother.
Browse our swimwear notions collection to find the clips, rings, sliders, elastic, lining, and support supplies you need for your next project. And if you’re not sure which notion is right for your pattern, contact us; we’re always happy to help you choose.
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