How to Make Your Own Swimwear

Regular elastic is not designed to withstand the harsh conditions that swimwear is exposed to, which is why it often breaks down quickly in chlorine, sunlight and salt water. What starts as supportive and flexible elastic can become brittle, stretched out or discoloured after just a few wears, leaving your swimsuit feeling loose and unsupportive. This happens because chlorine is an oxidising agent that breaks down the polymer structure in standard elastic, while UV exposure causes further degradation through photodegradation, and salt water adds additional stress that speeds up the process.

Swimwear elastic, on the other hand, is specifically designed to resist these conditions. It is usually made with synthetic cores such as polyester or nylon and finished with coatings that help protect against chlorine and UV damage, allowing it to maintain its stretch and recovery for much longer. There are several options to choose from depending on your project, including clear elastic for discreet internal support, coloured elastic when you want it to become part of the design, and fold-over elastic which creates a smooth, professional finish around edges without digging in or rolling. Choosing the right elastic makes a noticeable difference to how your swimwear performs over time, meaning your handmade pieces will last through many more swims rather than losing shape after just a few uses.

Regular universal needles are designed with a sharp point to pierce woven fabrics by pushing between intersecting threads. Swimwear fabric, however, is a knit, made from interlocking loops rather than a fixed weave. Because of this structure, a sharp needle can damage the fabric by piercing and distorting those loops instead of moving cleanly between them.

This is one of the main reasons skipped stitches happen when sewing swimwear. As the needle forces its way through the knit, it can catch or tear the loops rather than sliding through smoothly, which disrupts the formation of the stitch and prevents the needle from consistently picking up the bobbin thread. The result is uneven stitching and weak points in seams that need to be strong and flexible.

Stretch needles are designed specifically to solve this problem. They have a slightly rounded tip that allows them to pass between the loops of knit fabric rather than piercing them, helping to maintain the structure of the material. They also feature a specially designed scarf (the groove behind the eye of the needle), which helps the machine form stitches more reliably in stretch fabrics and reduces the chance of skipped stitches.

For most swimwear projects, a size 75/11 or 80/12 stretch needle is ideal. A finer needle reduces the risk of visible holes in delicate fabrics, while still being strong enough to handle the tension and elasticity of swimwear materials. Choosing the correct size is just as important as choosing the right type, as it directly affects both the appearance and durability of your finished garment.

In many cases, simply switching to the correct stretch needle is the difference between frustrating, inconsistent stitching and a smooth, professional finish that holds up well in wear and water.

Cotton thread is not suitable for swimwear because it simply isn’t designed to cope with the combination of stretch, moisture and chemicals that swimwear is exposed to. The main issue is that cotton thread has no stretch, while swimwear fabrics are designed to stretch significantly when worn. This creates tension in the seam every time the fabric moves, which can eventually lead to snapping or seam failure. Cotton is also highly absorbent, meaning it soaks up water during swimming, and it actually becomes weaker when wet, exactly when your garment needs it to perform at its strongest.

There is also a chemical factor to consider. Chlorine in swimming pools gradually breaks down cotton fibres by damaging their molecular structure, while salt water has a similar weakening effect over time. This means seams made with cotton thread can deteriorate much faster than expected, even if they initially appear strong and well-constructed.

Polyester thread is a far better choice for swimwear because it is engineered to withstand these conditions. It does not absorb water in the same way as cotton, maintains its strength whether wet or dry, and has enough flexibility to move with stretch fabrics without breaking. It is also more resistant to chlorine and salt water, making it far more durable for swimwear applications. For even greater strength and elasticity, woolly nylon thread can also be used, particularly in overlockers, where it creates soft, highly flexible seams that move comfortably with the body. In practice, switching from cotton to polyester thread can significantly extend the lifespan of your swimwear seams and improve the overall durability of your finished garment.

Swimwear fabric can be surprisingly slippery and difficult to control, especially when it’s folded or layered, which is why cutting in a single layer with a rotary cutter often gives far more accurate results. When stretchy fabric is folded and cut through two layers at once, the bottom layer can easily shift without you noticing, leading to pieces that don’t match up properly once you start sewing. This can cause fitting issues and unnecessary fabric waste, particularly in close-fitting garments like swimwear.

Using a rotary cutter helps solve this problem by allowing you to cut cleanly and smoothly without dragging the fabric out of position in the way scissors sometimes can. The rolling action of the blade glides through the fabric, keeping everything stable and reducing distortion during cutting. When used with a self-healing cutting mat, you also get a stable surface that protects your blade and helps you achieve much more precise results.

Working in single layers also gives you complete control over fabric placement, which is especially useful when working with prints or trying to maximise fabric yield. It allows you to see exactly how each pattern piece sits on the fabric, making it easier to align designs and avoid awkward placement. In the end, this approach helps ensure your pattern pieces match more accurately, giving your finished swimwear a cleaner, more professional look.

Straight stitches might look neat on the surface, but on swimwear fabric they create a rigid line that cannot move with the stretch of the fabric. When the garment is worn and the fabric expands, these fixed stitches become stress points, and over time they can snap or cause seams to fail.

Zigzag stitches are a much better option because they introduce built-in flexibility into the seam. The side-to-side motion of the stitch allows the thread to move as the fabric stretches, which helps the seam expand and contract without breaking. This makes zigzag stitching one of the most reliable methods for sewing swimwear on a standard sewing machine.

For even greater performance, many machines include specialist stretch stitches, often called lightning bolt stitches. These are designed specifically for highly elastic fabrics and create an even more flexible seam than a standard zigzag. They are particularly useful in high-stress areas such as side seams, leg openings and areas that experience a lot of movement.

Interestingly, flexible stitches like zigzag and stretch stitches are often stronger in swimwear than straight stitches because they distribute tension across the seam rather than concentrating it in a single rigid line. This helps prevent breakage and improves the overall durability of the garment.

As a general guide, a moderate zigzag stitch with a width and length of around 2–3mm works well for most swimwear seams. For areas that need extra stretch and recovery, switching to a dedicated stretch stitch will give a more secure and professional finish.

When sewing stretchy fabrics, the natural instinct is often to pull or stretch the fabric as you sew, but this usually causes more problems than it solves. Stretching the fabric while sewing puts tension into the seam, so when the garment is worn and the fabric relaxes, it can lead to wavy, puckered seams that don’t sit flat.

Your sewing machine is designed to feed fabric through at a steady pace using the feed dogs, and pulling the fabric works against this system. This can result in uneven stitches, tension issues and distorted seams.

The best approach is to guide the fabric gently while letting the machine do the work. Your role is to keep everything aligned, not to control the movement through the machine. For curved seams, simply help the fabric follow the shape without stretching it, allowing the fabric’s natural elasticity to do the shaping when the garment is worn.

This technique produces smooth, even seams that lie flat and behave properly on the body, giving a much more professional finish.

Lining your swimwear adds structure, support and longevity, helping the garment hold its shape much better over time. It acts like a built-in support layer, preventing the outer fabric from over-stretching and giving the swimsuit a more secure, stable feel when worn.

It also improves durability by distributing stress across two layers instead of one, which reduces strain on the outer fabric and helps the garment last longer with repeated wear. At the same time, lining creates a smoother, more comfortable interior against the skin, with added coverage and opacity that is especially useful for lighter colours or thinner swimwear fabrics.

Another benefit is protection. The lining acts as a subtle barrier between the body and the outer fabric, which can help reduce direct exposure to chlorine and other environmental stressors, supporting the longevity of both layers.

Visually and practically, lined swimwear also has a more polished, professional finish. It feels closer to ready-to-wear quality rather than a handmade garment, with better drape and stability.

For best results, use the same fabric for both outer and lining layers so the stretch and recovery remain consistent. Some sewists choose lighter lining fabrics, but matching fabric generally gives the most reliable performance and fit over time.

Skipping the iron is an important rule when sewing swimwear because most swimwear fabrics contain elastane or spandex fibres that are sensitive to heat. Even a moderately hot iron can permanently damage these fibres, reducing their ability to stretch and recover properly.

When exposed to heat, elastane can lose its elasticity and, in some cases, become permanently deformed. This may show up as shiny patches, flattened areas or a general loss of stretch, all of which affect both the fit and performance of the garment.

Instead of pressing with an iron, use your fingers to gently press seams open or to one side. The natural pressure and warmth from your hands is usually enough to shape the seam without risking damage to the fabric. This technique is simple but highly effective, especially with delicate stretch materials.

Steam can also be risky for some swimwear fabrics, as the combination of heat and moisture can relax fibres in a way that changes the fabric’s stretch and recovery. If heat is absolutely necessary, it should always be kept to a minimum, used with a pressing cloth, and tested on a fabric scrap first.

In practice, finger pressing often creates a softer, more flexible seam that works better with the natural movement of swimwear fabric than a sharp, heavily pressed finish.

Rinsing your swimwear after every swim is one of the most effective ways to protect it from long-term damage. Chlorine, salt, sunscreen and other chemicals don’t simply wash away on their own, they can linger in the fibres and continue to break down the fabric even after you’ve left the water.

Chlorine in particular continues to act as a bleaching and weakening agent while it remains in the fabric, which is why a quick rinse in fresh water straight after swimming is so important. Removing it early helps stop this ongoing chemical reaction and protects the structure of both the fabric and the elastane.

Sunscreen can also leave behind residues that may cause discolouration or gradual fabric breakdown over time, while salt water can crystallise as the fabric dries, creating tiny abrasive particles that slowly wear at the fibres. Rinsing removes both of these before they can cause lasting damage.

This simple step is especially important for preserving elastic performance, as elastane fibres are sensitive to prolonged exposure to harsh chemicals. By rinsing immediately after use, you significantly reduce this stress and help maintain the stretch and recovery of your swimwear.

It’s a quick habit that takes less than a minute, but it can dramatically extend the life of your handmade swimwear, keeping it looking better and fitting properly for much longer.

Creating beautiful, long-lasting swimwear at home isn't about having expensive equipment or years of experience. It's about understanding why these techniques work and applying them consistently. Each tip addresses a specific challenge that swimwear fabrics and construction present.

When you use high-stretch fabrics with proper elastic, cut carefully with the right tools, sew with appropriate needles and thread, use stretch-friendly techniques, and care for your finished garments properly, you're not just following rules – you're working with the unique properties of swimwear to create garments that perform as well as they look.

Your handmade swimwear can absolutely rival anything you'd buy in stores. The key is understanding the "why" behind each technique and applying these principles consistently. With the right materials, tools, and knowledge, you'll be creating swimwear that's not just beautiful, but built to last season after season.

Ready to dive in? With these foundations in place, you're equipped to create swimwear that's truly made to perform.