Period Swim Square Neck One-Piece - Last Call

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

Be there, be square, or be there in this cute square-neck style.
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 4.4 out of 5
Based on 11 reviews
  • 5 Stars
    9 Reviews
  • 4 Stars
    0 Reviews
  • 3 Stars
    0 Reviews
  • 2 Stars
    1 Review
  • 1 Star
    1 Review
82% 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 gizem e.
Verified Buyer
Band Size
30"
Pant Size
Teen 18-20
Size Purchased
L
Usage
  • Swim Class
Rated 5 out of 5

Great swimsuit

Bought it for my daughter who is swimming competitively. Provided great protection and she swam comfortably.

True to the size. It would be great if there were more design and color options z

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I recommend this product
Quality
Rated 1 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 Reiko K.
Verified Buyer
Band Size
N/A
Pant Size
Teen 00-2
Size Purchased
XS
Usage
  • Pool
Rated 5 out of 5

Perfect

We love this bathing suit. Perfect for swimming when you’re on your period and feeling confident while you’re wearing it!

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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 Stephanie P.
Verified Buyer
I'm a...
Adult
I purchased for...
A Teenager/Tween
Pant Size
Teen 4-10
Size Purchased
M
Band Size
N/A
Usage
  • Primary Protection
  • Period
Rated 5 out of 5

Great suit!

My kids love this suit! It fits well based on the sizing chart and is very comfortable. I would highly recommend.

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I recommend this product
Quality
Rated 5 out of 5
Comfort
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
Effectiveness
Rated 5 out of 5
Was this helpful?
Review posted
Reviewed by Dawn R.
Verified Buyer
I'm a...
Parental Figure
I purchased for...
A Teenager/Tween
Pant Size
Kids 16-20
Size Purchased
M
Band Size
N/A
Usage
  • Period
Rated 5 out of 5

Swimsuit

Got this for my daughter, it’s such an amazing swimsuit, keeps her protected!

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I recommend this product
Quality
Rated 5 out of 5
Comfort
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
Effectiveness
Rated 5 out of 5
Was this helpful?
Review posted
Reviewed by Melissa G.
Verified Buyer
Band Size
N/A
Pant Size
Teen 00-2
Size Purchased
XS
Usage
  • Pool
Rated 5 out of 5

Great suit!

This swimsuit saved summer camp this year! My daughter is not comfortable with tampons yet and got her period right before camp. She was able to still enjoy all the water activities of camp. Great quality. The built in period protection is discreet and slim. Not bulky. The cut was perfect for a teen. We tried another brand and the cut of that suit was too mature for my teen. This one was perfect.

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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 -1 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?