How Does Period Swimwear Work?

Swimming on your period has many benefits, including:

• Exercise lifts your mood and can help lessen PMS symptoms thanks to a release of endorphins
• Swimming can help relieve period cramps (menstrual cramps)
• Exercise reduces the fatigue associated with certain phases of your menstrual cycle

But more than that, there’s no reason you should have to experience FOMO while you’re on your period. 

The good news: Leakproof Swimwear is an all-in-one product that helps absorb menstrual blood and protect you from leaks. It’s also a stylish swimwear option for you to wear poolside, beachside, or lounging in your backyard. But how exactly does it work? Let’s dive in…

How Does Knix Period Swimwear Work?

Period swimwear (also known as Leakproof Swimwear or period-proof swimwear) is a relatively new offering. Basically, it leverages the same technology as period underwear with some added protection to make it work in water.

The best part? Just like period underwear, period swimwear looks just like regular swimwear and comes in a variety of styles, from bikini bottoms to one-pieces. You’ll even have a choice of color.

So how exactly does Knix period swimwear work? The layers in the gusset of the swimwear work to trap and absorb your period so it doesn't leak in the water (or on land!). Our Swimwear features the same Leakproof Technology as our Period Underwear with an additional thin layer of waterproof material for extra protection.

The inner layers help absorb blood and trap it, to help prevent leakage when you swim. When it goes in the laundry with mild detergent, it releases through the top layer— leaving your swim fresh and clean for tomorrow's laps.

Leakproof Swimwear has a super discreet absorbent pad in the gusset liner that absorbs about 3-6 teaspoons of blood or the equivalent of 3-5 regular tampons.

How Much Blood Will Period Swimwear Absorb?

Our period bathing suits will absorb up to 3 teaspoons of blood or menstrual fluid, which equals up to three tampons worth of menstrual blood.

Do I Have to Wear Other Period Protection (Like a Tampon or Menstrual Cup)?

It really depends on your unique flow! On lighter days, Leakproof Swimwear can be worn solo to help prevent leaks, while on heavier days, double up on protection and pair period swimwear with a disposable tampon or reusable menstrual cup. This can especially give you confidence on your heaviest flow day or while you’re getting used to period swimwear.

Our Leakproof Swimwear helps absorb menstrual blood on its own—around 3-5 tampons worth. You might want to start wearing it on your light-period days to build up your confidence. 

Is Period Proof Swimwear the Same as Period Underwear?

Period underwear and period swimwear share a lot of the same technology. However, there is one important difference: Period underwear is not designed to be worn in the water.

This means that you can’t simply swap those Leakproof Bikini Swim Bottoms for Super Leakproof Bikini underwear in a similar style. They may look identical, but one is designed to wear in the water, and the other is not. 

Does Period Swimwear Work for Other Leaks, Like Light Bladder Leaks?

Yes! Period swimsuits will absorb period blood. But it can also absorb sweat or urine (light bladder leaks.) So if you suffer from urinary incontinence, whether temporary or persistent, this is a great product to give you back some freedom and confidence. 

If you do experience light bladder leaks, know you’re not alone. Of the 25 million adult Americans suffering from some form of urinary incontinence, 75-80% of those are women. Pregnancy, childbirth, and menopause are major reasons for the increased prevalence of incontinence in women compared to men. 

Urinary incontinence is a complex topic (there are 5 kinds of urinary incontinence in women), so it’s definitely worth discussing with your doctor. However, products like Ultra Leakproof Zones+ and Leakproof Swimwear (aka period swimwear) can definitely make it easier to manage your day-to-day life while you explore treatment options.

Will People Be Able to Tell I’m Wearing Period Proof Swimwear?

Similar to the gusset on Leakproof Underwear, you may notice a slightly thicker gusset on your period swimwear. However, it will not be noticeable to other people, and you’ll likely forget it altogether once you get the swimwear on.

Period swimwear is designed to look just like regular swimwear. It comes in many different styles and colors. You can find:

• Two-piece swimsuits or one-piece period swimwear bottoms
• A variety of colors and patterns
• Simple maillot-style swimsuit, or ones with details like ruching, cut-outs, or wraparound
• Bikini bottoms that are classic bikini style, high-rise, or boyshorts style
• Swimsuits with other details like built-in shelf bras
• And so much more…

Basically, there’s something for everyone. And nobody will know the difference between your period swimsuit and any other swimsuit you might pick. Indeed, you might find yourself reaching for your period swimsuit even when you don’t have your period (which is great for those with irregular periods, too.)

Will I Leak Menstrual Blood?

Should you worry about leaving a blood trail in the water if your period products fail? It’s hard to make guarantees here: 50% of us have experienced a period product failing at some point. This is especially common at night.

The big difference is that at night, you may have exceeded your product’s absorbency limit. So, if you choose the right absorbency level for your flow and don’t push those limits, you should be fine. If you do have a very heavy menstrual flow, you may opt to use another menstrual product (e.g., a tampon or menstrual cup) for additional protection while you swim.

It is worth noting that the water pressure may lighten your blood flow, and even if you do leak a little, it will be quickly diluted in the water, so you’re unlikely to leave the gruesome blood trail that you’re probably picturing in your head.

How Do I Care for My Period Swimwear?

It couldn’t be easier: After your swim, just machine-wash the swimwear with mild detergent on a cold cycle and lay flat to dry. Do not use bleach or machine dry.

The Best Knix Period Swimwear for…

Ready to give period swimwear a try? Browse the full collection. If you’re a parent, there are also Period Swim options for teens. 

Want a little help? Here are some of our top picks.

Best for Classic Style: Leakproof Classic One Piece in Black

This is like a little black dress in swimsuit form. You can’t go wrong with this classic swimsuit style. The Leakproof Classic One Piece in Black has a hidden shelf bra for support, and its clean and sleek lines are universally flattering.

How it Fits: 

Smooth fit over the body with medium bum coverage. Fully lined with a no-dig leg opening, a built-in inner bra for support, and adjustable straps. This swimsuit comes in extended sizes that support bigger cups.

What Reviewers Say:

“I am a large chested curvy woman. I was drawn to this suit because it’s classic and yet looks modern. I feel comfortable and confident. I also love that it’s leakproof. Haven’t had to use it … but love that I’ll have backup coverage. I might wear this as a bodysuit this summer. Recommend. 16 top, 18 bottom XXL+ worked for me.”

Size Options: XS to XXXXL

Best for Flattering Fit: Leakproof High Rise Bikini Bottom

The Leakproof High Rise Bikini Bottom offers just the right amount of coverage, allowing you to feel confident and comfortable in your own skin. With additional sculpting properties for support, you can focus on having fun without worrying about wardrobe malfunctions.

How it Fits: 

A banded high-rise bottom with gentle tummy compression, flattering high-rise coverage, plus a built-in absorbent liner for confident period protection—about the same as 1-3 tampons. Ultra flattering silhouette is cut moderately on the leg and bum, with a no-dig leg opening.

What Reviewers Say:

“I bought a pair of these in solid black last year, and they became my go-to swim bottom. Even though I did not always wear for leak protection, I found that after a full day in and out of the water on hot days, I'd be less likely to have other issues develop because they wick away the moisture.”

Size Options: XS to XXXXL

Best for Retro Va-Va-Voom: Cinch Leakproof Shaper One Piece

With a sexy lace-up back and additional panels for contouring, this gorgeous Cinch Leakproof Shaper One Piece will have you feeling confident and comfortable!  PLUS a built-in absorbent liner for confident period protection –around 1-3 regular tampons worth.

How it Fits: 

The wrap top provides a customizable fit and look. The bottom half sits comfortably with slightly more than medium coverage on the thigh and bum.

What Reviewers Say:

“This is so comfortable and flattering. Very happy with this purchase and will be buying more colors for sure.”

Size Options: XS to XXXXL

Shop the full range of period swimwear here

FAQs on Period Swimwear

What is period swimwear?

If this is the first you’ve heard of Period Swimwear, know that it’s a relatively new innovation spurred by girls and women looking for period products that are tailored towards certain activities for optimal comfort. 

Leakproof Swimwear has a multi-layered gusset built into its period swim bottoms and one-pieces that helps trap and absorb period blood. It’s similar to the absorbent technology used in Leakproof Underwear (also known as period underwear). 

And, just like period underwear, the absorbent gusset is discreet and comfy, which means you don’t even need to be on their period to wear them. Period Swim is designed to feel just like regular swimwear—it’s just equipped with helpful gear that helps lock blood in, keep water out, and never swell.

How does period swimwear absorb blood but not water?

Leakproof Swimwear has a multi-layered gusset built into its period swim bottoms and one-pieces that trap and absorb period blood. It’s similar to the absorbent technology used in Leakproof Underwear (also known as period underwear). 

Can you swim with just period swimwear?

It really depends on your unique flow! On lighter days, Leakproof Swimwear can be worn solo to help prevent leaks, while on heavier days, double up on protection and pair period swimwear with a disposable tampon or reusable menstrual cup. This can especially give you confidence on your heaviest flow day or while you’re getting used to period swimwear.

Leakproof Swimwear absorbs around 3-5 tampons of menstrual blood. You might want to start wearing it on your light-period days to build up your confidence.

Related articles: Can you swim when your on your period? or How do swimmers swim on their period?