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KnixTeen

Teen Period Swim Square Neck One-Piece

$88.00 USD

Absorbs about 2-3 regular tampons

Full coverage style

Flattering square neckline

Premium UPF 50+ fabric

Machine washable

Front view of model wearing the Teen Period Swim Square Neck One-Piece highlighting the coverage and fit
Teen Period Swim Square Neck One-Piece shown front-facing against a light gray background
Back view of model wearing the Teen Period Swim Square Neck One-Piece highlighting the coverage and fit
Front view of model wearing the Teen Period Swim Square Neck One-Piece highlighting the coverage and fit
Front view of model wearing the Teen Period Swim Square Neck One-Piece highlighting the coverage and fit
Close-up of gusset

Color: Black

Size:

True to Size

•

Size:

Size and Fit Guide

Free Shipping on orders $100+

Shipping

Shipping

Processing Timelines

Please allow 1-2 business days for our warehouse team to pack and ship your order. During peak periods such as sales, holidays and product launches, please allow up to 4 business days for us to process your order. Once an order is placed, we cannot guarantee any address updates, order changes or cancellations. Orders placed on Friday after 1PM will not be shipped until the following Monday.


Split Shipments

Most orders will ship from a single warehouse. However, we occasionally ship from a combination of warehouse locations, so you may receive your order in multiple parts. If items from your order ship in separate packages, we’ll send you tracking information for each package when it becomes available.

Delivery Timelines

For the most up-to-date delivery time estimates, please refer to the shipping timeline at checkout. Delivery timelines do not include processing times. See above for details. All transit times are measured in business days which are Monday-Friday, excluding holidays.

Please note, all shipping timelines are estimates and are not guaranteed.

We are not able to ship to US territories (including Puerto Rico, U.S. Virgin Islands, Guam, Northern Mariana Islands and American Samoa) at this time.

Easy Returns within 30 Days

Apparel, Sleep & Swim

Returns & Exchanges

Holiday Return Policy
Eligible items purchased online or in stores between November 2, 2026 and December 31, 2026 may be returned through January 29, 2027. All other purchases fall under our 30 day Returns Policy.

Standard Return Policy
Apparel (excluding Shapewear), sleep and swim are eligible for return or exchange within 30 days of delivery with tags attached. Swim bottoms and one-pieces must have the original sanitary strip intact.

Still have questions? View our full policy here.

Rewards Members Earn 88 Points

Product Description

Enjoy swim days with confidence, even on your period, with the Teen Period Swim Square Neck One‑Piece, a leak‑fighting moderate‑absorbency swimsuit that absorbs about the equivalent of 2-3 regular tampons, features a sporty square neckline with built‑in shelf bra and removable cups, and is crafted from premium UPF 50+ fabric that protects your skin while you swim or play in the sun — fully machine‑washable with discreet built‑in protection that looks and feels like regular swimwear.

Swim in Style

A sporty style with a square neckline, built-in shelf bra and removable cups.

Worry-Free Protection

Discreet, built-in protection that absorbs about 2-3 regular tampons worth.

Sun-Smart Protection

UPF 50+ fabric protects your skin while you soak up the sun.

Zoom

How to Choose?

Essential

  • • Days you don’t need leak protection. Everyday freshness and moisture wicking.
  • tsp
    0 tsp

Heavy

  • • Extra peace of mind. For the first days of your cycle, light bladder leaks, or a full night's sleep without a leak.
  • tsp
    about 8-14 tsp
  • pad
    about 1.5-3 regular pads
  • tampon
    about 4-7 super tampons
  • cup
    about 1.5-3 menstrual cups

Light

  • • Daily freshness. For sweat, discharge, period spotting, or backup protection.
  • tsp
    about 1-3 tsp
  • pad
    about 1-3 pantyliners
  • tampon
    about 1-3 regular tampons
  • cup
    about 0.5 menstrual cups

Moderate

  • • For mid-cycle flow, surprise cough or sneeze leaks, or a really sweaty spin class.
  • tsp
    about 4-8 tsp
  • pad
    about 1-1.5 regular pads
  • tampon
    about 2-4 super tampons
  • cup
    about 0.5-3 menstrual cups

Ultra

  • • Ultimate peace of mind. For the heaviest period days, light bladder leaks, unexpected postpartum flow, or overnight protection.
  • tsp
    about 15-20 tsp
  • pad
    about 1.5-2.5 super pads
  • tampon
    about 7-11 super tampons
  • cup
    about 2-3 menstrual cups
LEAKPROOF SWIM WORKS IN LAYERS

Built-in protection that feels like nothing at all.

Looks just like regular swimwear. Non-swelling liner and patented no-show design.

Top Layer

Smooth and comfortable liner in swimsuit fabric.

4.6
Rated 4.6 out of 5 stars
Based on 63 reviews
What our customers are saying
Customers say this swimsuit fits true to size and provides comfortable, flattering coverage for tweens and teens. Many reviews mention the adjustable straps and modest cut that works well for young swimmers. Parents frequently praise how the suit gives their daughters confidence during swimming activities. Common feedback includes appreciation for the supportive shelf bra and quality construction. While most find the fit perfect, some suggest sizing up for longer torsos or prefer more coverage in the back area. A few mention strap durability concerns after extended wear.
87%would recommend this product
ComfortRated 4.7 on a scale of 1 to 5
FitRated -0.2 on a scale of minus 2 to 2
EffectivenessRated 4.7 on a scale of 1 to 5
Keywords
Keywords
Rating
Ratings
Height
Height
Usual Pant Size - Knixteen
Usual Pant Size - Knixteen
63 reviews
  • Rated 5 out of 5 stars
    4 minutes ago
    Love!

    My daughter loves it. Super cute and comfortable.

    FM
    Fallon M.
    Verified Buyer
    Reviewing
    Teen Period Swim Square Neck One-Piece
  • Rated 5 out of 5 stars
    3 months ago
    5 Stars

    My daughter really liked her bathing suit. She felt comfortable on it.

    C
    Cristian
    Reviewing
    Teen Period Swim Square Neck One-Piece
  • Rated 5 out of 5 stars
    3 months ago
    Good Swim Suit

    My daughter loves this swimsuit!

    She says it comfy.

    It fits right.

    The colors are BEAUTIFUL

    K Profile picture for Knix
    Knix
    3 months ago

    Hey Stella!

    We're so thrilled to hear your daughter loves her Teen Period Swim! The fit and comfort sound perfect, and those colors really are gorgeous!

    Team Knix

    SA
    Stella A.
    Verified Buyer
    Reviewing
    Teen Period Swim Square Neck One-Piece
  • Rated 5 out of 5 stars
    4 months ago
    Swimsuit for tween

    My daughter loves this suit. Super comfortable and soft material.

    AW
    Andrea W.
    Verified Buyer
    Reviewing
    Teen Period Swim Square Neck One-Piece
  • Rated 5 out of 5 stars
    4 months ago
    Worked great

    My daughter wore this in Florida while on vacation. She was a little skeptical at first, because, how could it work?! But it did and it made her vacation that much better. Not having to tell silly boys why you can’t swim is embarrassing enough.

    K Profile picture for Knix
    Knix
    4 months ago

    Hey Carole!

    This is so wonderful to hear! We're thrilled your daughter had an amazing vacation without any worries. That's exactly what we designed this swimsuit for!

    Team Knix

    CR
    Carole R.
    Verified Buyer
    Reviewing
    Teen Period Swim Square Neck One-Piece
  • Rated 3 out of 5 stars
    5 months ago
    “Feels Weird”

    My daughter wore this for the first time to her swimming lessons yesterday and I’m thinking it’s perhaps the wrong size. She complained that it “felt weird” as it was saggy in the bum area.

    We followed the size chart and thought about ordering a smaller size to try as there was some gaping in the chest, however it seemed like too much of a hassle so we opted to keep the medium as it seemed to fit everywhere else fine.

    The fabric quality and colour are both beautiful.

    We love knix products and haven’t given up on their swim yet - just feeling mixed on this specific swimsuit right now!

    DR
    Dannielle R.
    Verified Buyer
    Reviewing
    Teen Period Swim Square Neck One-Piece
  • Rated 5 out of 5 stars
    5 months ago
    My teen loves it.

    Fits well and my teen approves!

    SF
    Shireen F.
    Verified Buyer
    Reviewing
    Teen Period Swim Square Neck One-Piece
  • Rated 5 out of 5 stars
    5 months ago
    5 Stars

    Very cute! Fir my daughter perfectly!

    C
    Courtney
    Reviewing
    Teen Period Swim Square Neck One-Piece
  • Rated 3 out of 5 stars
    6 months ago
    Loose top

    The top was loose while swimming. It did work for controlling the period.

    SI
    Sonia I.
    Verified Buyer
    Reviewing
    Teen Period Swim Square Neck One-Piece
  • Rated 5 out of 5 stars
    11 months ago
    Good fit!

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

    CC
    Chir C.
    Verified Buyer
    Reviewing
    Teen Period Swim Square Neck One-Piece
  • Rated 5 out of 5 stars
    11 months ago
    Good fit!

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

    CC
    Chir C.
    Verified Buyer
    Reviewing
    Teen Period Swim Square Neck One-Piece
  • Rated 5 out of 5 stars
    1 year ago
    Lovely fit and comfortable

    Functions as described and has a flattering and comfortable fit.

    CB
    Chanta B.
    Verified Buyer
    Reviewing
    Teen Period Swim Square Neck One-Piece