Period Swim Square Neck One-Piece

Not into tampons or cups? No biggie. As sleek as it is powerful, this one-piece was designed with a higher neckline, thin straps, a built-in shelf bra, and our discreet leak-fighting liner. For added customization, keep in or take out the removable cups—the choice is always yours.


First layer: A silky-smooth layer that sits comfortably against the skin.

Second layer: Holds up to 3 pads’ or tampons’ worth of blood.

Third layer: A secure, liquid-resistant layer that prevents leaks.

Other Features:

- Bum coverage: Full

- Removable cups

- Fully lined

- Super-discreet liner

- 50+ UPF protection

Swim with confidence on your period in this sporty, leakproof one-piece.
Image of a absorbancy surrounding text
Holds up to 3 pads’ worth of blood
Image of a moisture fabric surrounding text
Rapidly absorbs moisture to keep you fresh and dry all day.
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.

Not into tampons or cups? No biggie. As sleek as it is powerful, this one-piece was designed with a higher neckline, thin straps, a built-in shelf bra, and our discreet leak-fighting liner. For added customization, keep in or take out the removable cups—the choice is always yours.


First layer: A silky-smooth layer that sits comfortably against the skin.

Second layer: Holds up to 3 pads’ or tampons’ worth of blood.

Third layer: A secure, liquid-resistant layer that prevents leaks.

Other Features:

- Bum coverage: Full

- Removable cups

- Fully lined

- Super-discreet liner

- 50+ UPF protection

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
COMFORTABLE
JUST PLAIN BETTER
REUSABLE
COMFORTABLE
JUST PLAIN BETTER
REUSABLE
COMFORTABLE
JUST PLAIN BETTER
Reviews
average rating 4.3 out of 5
Based on 21 reviews
  • 5 Stars
    17 Reviews
  • 4 Stars
    0 Reviews
  • 3 Stars
    0 Reviews
  • 2 Stars
    1 Review
  • 1 Star
    3 Reviews
81% 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 Chir C.
Verified Buyer
I'm a...
Parental Figure
I purchased for...
A Teenager/Tween
Current Band Size
28
Pant Size
Kids 12-14
Size Purchased
M
Usage
  • Pool
  • Swim Class
  • Beach
Rated 5 out of 5

Good fit!

This is a good fit. The cut offers great coverage. Washes well.

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I recommend this product
Quality
Rated 4 out of 5
Comfort
Rated 5 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
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Review posted
Reviewed by Chanta B.
Verified Buyer
I'm a...
Parental Figure
I purchased for...
A Teenager/Tween
Current Band Size
28
Pant Size
Kids 12-14
Size Purchased
S
Usage
  • Swim Class
Rated 5 out of 5

Lovely fit and comfortable

Functions as described and has a flattering and comfortable fit.

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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
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Review posted
Reviewed by Heather G.
Verified Buyer
Band Size
N/A
Pant Size
Teen 12-16
Size Purchased
L
Usage
  • Beach
  • Pool
Rated 5 out of 5

Perfect fit!

The suit fits true to size and you would never know it is reinforced. It’s quite modest as well. The adjustable straps are a great option.

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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
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Review posted
Reviewed by Christina P.
Verified Buyer
Band Size
34"
Pant Size
Teen 12-16
Size Purchased
M
Usage
  • Pool
  • Swim Class
  • Beach
  • Sun Bathing
Rated 5 out of 5

Period Swim Square Neck One-Piece

This is great for my 11-year old for swimming!

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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 Heather G.
Verified Buyer
I'm a...
Parental Figure
I purchased for...
A Teenager/Tween
Current Band Size
34
Pant Size
Teen 4-10
Size Purchased
M
Rated 5 out of 5

Great teen swimsuit

Fits as described

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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?