Period Swim Sport One-Piece

The one-piece that keeps selling out! Perfect for all swimmers, it can be worn alone on light days, or with a tampon or menstrual cup on heavy days, and won’t leak whether you’re in or out of the water. Designed with three layers to keep you cool, calm, and protected:

Layer 1: A silky-smooth top layer that sits comfortably against the skin.

Layer 2: A highly-absorbent middle layer designed with our leakproof technology to absorb about 2 super tampons worth of period blood.

Layer 3: A waterproof outer layer prevents swelling.


Other Features:

- Fully lined

- Open racerback for better mobility

- Removable cups

- Bum coverage: Medium

- Super-discreet liner

- 50+ UPF protection

- Seawater and chlorine resistant

The #1 essential for swimming freely and fearlessly on your period.
Image of a absorbancy surrounding text
Absorbs about 2 super tampons worth of blood.
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Rapidly absorbs moisture to keep you fresh and dry.
Image of a light and comfy surrounding text
Thin, subtle, and designed to feel just like regular swimwear.
Image of a machine washable surrounding text
Simply machine wash cold and lay flat to dry.

The one-piece that keeps selling out! Perfect for all swimmers, it can be worn alone on light days, or with a tampon or menstrual cup on heavy days, and won’t leak whether you’re in or out of the water. Designed with three layers to keep you cool, calm, and protected:

Layer 1: A silky-smooth top layer that sits comfortably against the skin.

Layer 2: A highly-absorbent middle layer designed with our leakproof technology to absorb about 2 super tampons worth of period blood.

Layer 3: A waterproof outer layer prevents swelling.


Other Features:

- Fully lined

- Open racerback for better mobility

- Removable cups

- Bum coverage: Medium

- Super-discreet liner

- 50+ UPF protection

- Seawater and chlorine resistant

Machine wash cold and lay flat to dry. Do not bleach, iron, or dry clean.


Body: 85% Nylon, 15% Spandex

Lining: 85% Nylon, 15% Spandex

Gusset: Fresh Fix Technology®, Polyurethane Film


Additional Product Ingredient Information

For items with a 20% or more discount, you may exchange for another item or return for store credit. No refunds can be accommodated. 

Items marked as “Flash Sale” or “Clearance” are final sale, meaning no returns, exchanges or refunds can be accommodated. No exceptions. 

Please note: Sale items are not eligible for our First Pair Risk-Free Policy.


We offer free standard shipping on all orders over $70. We ship our items via DHL or Canada Post depending on your location. Please allow 1-2 business days for your items to be processed and shipped. During high volume periods, your order may take up to 7 business days to dispatch from our warehouse location.


US Orders: Please allow 3–10 business days for orders to arrive.

International Orders: Please allow 10–25 business days for orders to arrive.

NOTE: Orders placed on Friday after 1 PM will not be processed until the following Monday.

CANADIAN CUSTOMERS: Shop www.knixteen.ca to order in Canadian currency.

 FOR THE PLANET
FOR REAL LIFE
FOR THIS GENERATION
FOR THE PLANET
FOR REAL LIFE
FOR THIS GENERATION
FOR THE PLANET
FOR REAL LIFE
FOR THIS GENERATION
FOR THE PLANET
FOR REAL LIFE
FOR THIS GENERATION
FOR THE PLANET
FOR REAL LIFE
FOR THIS GENERATION
FOR THE PLANET
FOR REAL LIFE
FOR THIS GENERATION
FOR THE PLANET
FOR REAL LIFE
FOR THIS GENERATION
FOR THE PLANET
FOR REAL LIFE
FOR THIS GENERATION
FOR THE PLANET
FOR REAL LIFE
FOR THIS GENERATION
FOR THE PLANET
FOR REAL LIFE
FOR THIS GENERATION
FOR THE PLANET
FOR REAL LIFE
nothing is TMI here—we promise.

Our period swim bottoms contain a triple-layer gusset that absorbs your flow and locks in leaks, whether you're in or out of the water. When they go in the wash with detergent, the blood releases through the top layer—leaving your swimwear fresh and clean for next time. Yes, your other clothes will remain stain-free!

Here's the breakdown of our 3-layer leakproof technology:

Layer 1: A silky-smooth top layer that sits comfortably against the skin.

Layer 2: A highly-absorbent middle layer designed with our leakproof technology to absorb up to 1-3 tampons worth of period blood.

Layer 3: A waterproof outer layer prevents swelling. 

Not always. When your flow is light, our swimwear can be worn alone without any additional period protection. On super heavy days, we recommend wearing a tampon or menstrual cup with your swimwear. Every period is different though, and we recommend doing whatever makes you feel most confident.

Machine wash cold and lay flat to dry. Do not bleach, iron, or dry clean.

Check out our size chart here. 

Yes! All of our regular price swim bottoms and one-pieces are eligible for a return or exchange within 30 days of delivery, as long as the original sanitary strip and tags are attached. Our swim tops are eligible for a return or exchange within 30 days of delivery with original tags attached.

Absolutely! The leakproof liner built into all of our period swimwear is undetectable, so they look and feel just like regular swimwear.

Our styles are made to fit teen bodies. For period swimwear in adult sizes, please visit Knix.

 COMFORTABLE
JUST PLAIN BETTER
REUSABLE
COMFORTABLE
JUST PLAIN BETTER
REUSABLE
COMFORTABLE
JUST PLAIN BETTER
REUSABLE
COMFORTABLE
JUST PLAIN BETTER
REUSABLE
COMFORTABLE
JUST PLAIN BETTER
REUSABLE
COMFORTABLE
JUST PLAIN BETTER
REUSABLE
COMFORTABLE
JUST PLAIN BETTER
REUSABLE
COMFORTABLE
JUST PLAIN BETTER
REUSABLE
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JUST PLAIN BETTER
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JUST PLAIN BETTER
Reviews
average rating 4.4 out of 5
Based on 307 reviews
  • 5 Stars
    216 Reviews
  • 4 Stars
    44 Reviews
  • 3 Stars
    23 Reviews
  • 2 Stars
    5 Reviews
  • 1 Star
    19 Reviews
87% of reviewers would recommend this product to a friend
Quality
Rated 4 out of 5
Comfort
Rated 4 out of 5
Effectiveness
Rated 4 out of 5
Sizing
Rated 0 on a scale of minus 2 to 2, where minus 2 is Fits Small, 0 is True to Size and 2 is Fits Large
Write a Review
Review posted
Reviewed by Angela P.
Verified Buyer
Period Swim Sport One-Piece
Reviewing
Period Swim Sport One-Piece
Band Size
32"
Pant Size
Teen 4-10
Size Purchased
M
Usage
  • Pool
  • Swim Class
  • Beach
  • Sun Bathing
Rated 5 out of 5

Great for school swimming

This is just what my daughter needed for her swimming PE class. It fits great and isn’t skimpy. She’s stoked.

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I recommend this product
Quality
Rated 5 out of 5
Comfort
Rated 4 out of 5
Effectiveness
Rated 5 out of 5
Sizing
Rated 0 on a scale of minus 2 to 2, where minus 2 is Fits Small, 0 is True to Size and 2 is Fits Large
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Review posted
Reviewed by Genevieve C.
Verified Buyer
Period Swim Sport One-Piece
Reviewing
Period Swim Sport One-Piece
I'm a...
Parental Figure
I purchased for...
A Teenager/Tween
Band Size
28"
Pant Size
Teen 00-2
Size Purchased
S
Usage
  • Swim Class
  • Pool
  • Beach
Rated 5 out of 5

Super!!

Ma fille trouve le maillot vraiment confortable. Elle est très heureuse puisqu’elle pourra faire ses cours de piscine à l’école sans encombre. Le maillot est très beau et fait très bien.

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I recommend this product
Quality
Rated 5 out of 5
Comfort
Rated 5 out of 5
Effectiveness
Rated 5 out of 5
Sizing
Rated 0 on a scale of minus 2 to 2, where minus 2 is Fits Small, 0 is True to Size and 2 is Fits Large
Was this helpful?
Review posted
Reviewed by Kristin A.
Verified Buyer
Period Swim Sport One-Piece
Reviewing
Period Swim Sport One-Piece
I'm a...
Parental Figure
I purchased for...
A Teenager/Tween
Band Size
N/A
Pant Size
Kids 12-14
Size Purchased
XS
Usage
  • Swim Class
  • Pool
  • Beach
  • Sun Bathing
Rated 5 out of 5

Best suit ever

This suit fit my daughter perfectly. She is a competitive swimmer and this suit was comfortable and made her feel confident while on her period

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I recommend this product
Quality
Rated 5 out of 5
Comfort
Rated 5 out of 5
Effectiveness
Rated 5 out of 5
Sizing
Rated 0 on a scale of minus 2 to 2, where minus 2 is Fits Small, 0 is True to Size and 2 is Fits Large
Was this helpful?
Review posted
Reviewed by megan p.
Verified Buyer
Period Swim Sport One-Piece
Reviewing
Period Swim Sport One-Piece
I'm a...
Parental Figure
I purchased for...
A Teenager/Tween
Band Size
N/A
Pant Size
Kids 16-20
Size Purchased
M
Usage
  • Pool
  • Beach
Rated 5 out of 5

Amazing product!

Works perfectly! Gave my daughter the confidence to swim with her first period and allowed her to have fun and be a kid without any worries! Highly recommend

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I recommend this product
Quality
Rated 5 out of 5
Comfort
Rated 5 out of 5
Effectiveness
Rated 5 out of 5
Sizing
Rated 0 on a scale of minus 2 to 2, where minus 2 is Fits Small, 0 is True to Size and 2 is Fits Large
Was this helpful?
Review posted
Reviewed by Linda L.
Verified Buyer
Period Swim Sport One-Piece
Reviewing
Period Swim Sport One-Piece
I'm a...
Parental Figure
I purchased for...
A Teenager/Tween
Band Size
N/A
Pant Size
Teen 12-16
Size Purchased
L
Rated 5 out of 5

Black one piece

My granddaughter loves knix bathing suits. She wears it even if she s not on her periods . She says, they are the most comfortable bathing suits . She's a lifeguard/instructor and she only wants to wear knix bathing suits.

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I recommend this product
Quality
Rated 5 out of 5
Comfort
Rated 5 out of 5
Effectiveness
Rated 5 out of 5
Sizing
Rated 0 on a scale of minus 2 to 2, where minus 2 is Fits Small, 0 is True to Size and 2 is Fits Large
Was this helpful?