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Bonnie Adjustable Period Swim Bottom
  • Bonnie Adjustable Period Swim Bottom
  • Bonnie Adjustable Period Swim Bottom
  • Bonnie Adjustable Period Swim Bottom
  • Bonnie Adjustable Period Swim Bottom
  • Bonnie Adjustable Period Swim Bottom
  • Bonnie Adjustable Period Swim Bottom
  • Bonnie Adjustable Period Swim Bottom
  • Bonnie Adjustable Period Swim Bottom
  • Bonnie Adjustable Period Swim Bottom
  • Bonnie Adjustable Period Swim Bottom
  • Bonnie Adjustable Period Swim Bottom
  • Bonnie Adjustable Period Swim Bottom
Bonnie Adjustable Period Swim Bottom
★★★★★ (128)

Bonnie Adjustable Period Swim Bottom

£29.90 £39.90-25%
Absorbency: High
Choose your style
Esme High-Waist Period Swim Bottom
Elsie Period Swim Bottom
Darcie Seamless Period Swim Bottom
Bonnie Adjustable Period Swim Bottom
Color : Black
Size

Size guide

SIZEEquivalentWaist (cm)Hips (cm)
XS12-14 yrs59-6379-84
S3464-6884-89
M3669-7389-94
L3874-7994-100
XL4080-85100-106
XXL4286-92106-113
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30-day guarantee Free exchange Secure payment

Leak-proof and odour-free

Up to 12h of protection

Machine washable

30° without fabric softener

Reusable

For 5 to 7 years

Ultra-discreet protection

No bulky feel

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Description

The Sybille period swimsuit lets you swim with total peace of mind during your period, with no tampon or cup. Its patented 4-layer technology absorbs the equivalent of 3 tampons while staying 100% invisible — indistinguishable from a regular swimsuit.

Designed with textile engineers and gynaecologists, tested in chlorinated pools and seawater.

Shipping & returns

Delivery: Ships within 5 to 7 business days to the UK. Free shipping on orders over £60.

Returns: 30-day satisfied-or-refunded guarantee — even worn, even washed. If the size does not fit, free exchange. Contact us via the form on our website.

How to wash it?
  1. Rinse in cold water until the water runs clear
  2. Wash at 30°C in the machine or by hand with your usual detergent
  3. Dry in open air (4 to 6h)

No fabric softener, no tumble dryer, no bleach — to preserve the absorbent technology.

Benefits
  • Ultra comfortable — nothing to insert, zero chafing
  • Absorbs the equivalent of 3 tampons, up to 12h
  • 100% invisible — no extra layer, no string
  • Odour-free and antibacterial
  • Resistant to chlorine, salt and UV
  • Reusable for 5 years — 1,000+ tampons saved
Composition

Outer: 86% recycled nylon, 14% elastane — soft, chlorine-resistant, eco-friendly.

Built-in 4-layer technology:

  1. Fast-absorption layer — wicks moisture away from the skin
  2. Storage layer — microfibres that trap liquid
  3. Waterproof membrane — nothing gets out, nothing gets in
  4. Outer layer — UV50+ protection, chlorine/salt resistant
Durability

On average, a person uses 17,000 disposable products over their menstrual life — that much plastic waste ending up in the oceans.

A single Sybille swimsuit, used for 5 years, replaces around 1,000 tampons. Washable, reusable, no single-use plastic. It's good for you and for the planet.

What our founder is saying

Why choose us? 🏆

Buy 2, Get 1 Free! ⌛

0 Leaks Guaranteed 🩸

For Teens & Adults.

Discover our other bottoms

Esme High-Waist Period Swim Bottom
Esme High-Waist Period Swim Bottom £39.90£29.90
Darcie Seamless Period Swim Bottom
Darcie Seamless Period Swim Bottom £39.90£29.90
Bonnie Adjustable Period Swim Bottom
Bonnie Adjustable Period Swim Bottom £39.90£29.90
Elsie Period Swim Bottom
Elsie Period Swim Bottom £39.90£29.90

Loved by women across the UK

Trustpilot · Rated Excellent on Trustpilot · 2,140 reviews
Emma W. 🇬🇧 UK · 1 review 2 days ago

Finally swim with total confidence

Wore these for my whole holiday and never once worried about leaks. Completely invisible under my swimsuit and so comfortable.

Verified purchase
Charlotte H. 🇬🇧 UK · 1 review 4 days ago

A game changer for the pool

Absorbent, discreet and no bulky feeling whatsoever. I can finally swim on my period without a single worry.

Verified purchase
Olivia B. 🇬🇧 UK · 1 review 1 week ago

Brilliant quality

The fabric feels lovely and holds up beautifully wash after wash. Genuinely the best menstrual swimwear I've tried.

Verified purchase
Sophie M. 🇬🇧 UK · 1 review 1 week ago

No more skipping the beach

I used to dread swimming on my period. These changed everything — secure, soft and you truly cannot tell.

Verified purchase
Grace T. 🇬🇧 UK · 1 review 2 weeks ago

Comfortable and reliable

Stayed perfectly in place while swimming and snorkelling. Zero leaks and they dried quickly too. Highly recommend.

Verified purchase
Hannah L. 🇬🇧 UK · 1 review 3 weeks ago

Honestly so discreet

You honestly cannot tell these are period swimwear. Flattering fit and brilliant protection — worth every penny.

Verified purchase
Amelia R. 🇬🇧 UK · 1 review 3 weeks ago

Perfect for my teenager

Bought a pair for my daughter and she finally feels confident swimming at school. Thank you Henriette!

Verified purchase
Jessica P. 🇬🇧 UK · 1 review Last month

Wish I'd found these sooner

Light, secure and absolutely invisible under my bikini. I've already ordered a second pair.

Verified purchase

As featured in

Gala
Elle
Vogue
Brut
Marie Claire
Femme Actuelle
Doctissimo

What a Sybille swimsuit does better.

Developed with textile engineers and gynaecologists: as thin as a regular swimsuit, with the best absorption on the market.

Find your perfect swimsuit

Which period swimsuit is right for you?

Answer 2 questions and discover the style that suits your body and your flow.

Question 1 / 2

What protection do you usually use on a typical period day?

Question 2 / 2

On your heaviest days, how often do you change your protection?

Your result

Swim on your period.
No mental gymnastics.
  • 12h of protection in the water
  • 3× a tampon's absorption
  • 0 leaks — 30-day guarantee
  • 4 yrs of research & development

Summer Lookbook

Free to do everything, even when it's that time of the month

Our customers, captured in the moment. No stress, no compromise, just the joy of the water.

The sea, no calendar neededAt the beach01

The sea, no calendar needed

The only thing on your mind is the water temperature. Not your period. Not a string. Not the time.

You go in when you want. You come out when you want. Without asking yourself a single question.

"I finally got to jump in the waves without overthinking everything."

— Julie 🇬🇧
A full day, without a second thoughtAt the pool02

A full day, without a second thought

You swim. You sunbathe. You have lunch. You dive back in. The absorbent lining holds for up to 12h in the water — three layers, waterproof membrane, zero feeling of dampness.

You put it on in the morning. You didn't think about it again.

This year, your period doesn't decide your plansOn holiday03

This year, your period doesn't decide your plans

No more checking the period app before booking. No more crossing your fingers. No more plan B.

You go. That's it.

"This is literally what saved my last holiday."

— Isalu 🇬🇧
So she can live this summer like all her friendsFrom age 1204

So she can live this summer like all her friends

You remember that feeling. Sitting on the towel while everyone else was swimming.
She won't have to remember it.

No tampon. Nothing to insert. Nothing to explain. Sizes from age 12 — made for her.

4.9 Based on 128 reviews
5 116
4 8
3 2
2 1
1 1
Isla M. Verified purchase
2 October

Finally swim on my period with zero worries

I was so nervous about wearing a swimsuit during my period on holiday, but these bottoms were a total game-changer. No leaks at all and the fit is lovely. Wish I'd found them sooner!

Freya B. Verified purchase
24 September

Brilliant for the pool

Comfortable, flattering and genuinely leak-proof. I've worn them swimming twice now and felt completely secure. The colour is gorgeous too.

Poppy H. Verified purchase
15 September

Perfect for my daughter's swimming lessons

Bought these for my teenage daughter and she's so much more confident at her swimming lessons now. Lovely quality and they wash brilliantly.

Ruby C. Verified purchase
3 September

Worth every penny

Was sceptical at first but these are excellent. Discreet, comfy and no faffing with tampons at the beach. Highly recommend.

Lucy A. Verified purchase
27 August

So comfy I forget I'm wearing them

The fabric is so soft and the high waist is really flattering. I felt secure all day at the lido.

Daisy W. Verified purchase
12 August

Great fit and reassuring

True to size and the protection is spot on. Took them on a girls' trip to Spain and didn't worry once.

Florence K. Verified purchase
30 July

An absolute must-have

I have heavy periods and was worried, but no leaks whatsoever. The customer service was lovely too.

Maisie T. Verified purchase
18 July

Couldn't be happier

Beautiful swimwear that actually works. Already ordering the matching top!

Evie R. Verified purchase
5 July

Exceeded my expectations

Delivery was quick and the quality is far better than I expected. These are now my go-to for the pool.

Everything you need to know before buying

Your questions, our answers

Product & Performance

Does it REALLY work in a swimming pool?
Yes. That's the fundamental difference from regular period underwear: the waterproof layer is designed to withstand prolonged immersion in chlorinated pools and sea water. Tested by our customers over full days with no leaks reported.
What flow level does it work for?
Perfect for moderate to heavy flow (equivalent to 2–3 tampons). For a very heavy flow, our honest recommendation: combine with a cup or change between swims.
Is it really invisible under the swimsuit?
Yes, completely. The 4-layer technology is as thin as a regular swimsuit. No creases, no visible thickness, even under a fitted light-coloured swimsuit.
What is the swimsuit made of?
Bottoms are made of 86% recycled Nylon and 14% Elastane — soft, chlorine-resistant and eco-friendly. Tops are 82% Polyamide and 18% Elastane for optimal support. The intimate lining features our patented Sybille® 4-layer technology.
What's the difference from regular period underwear?
Regular period underwear absorbs but isn't designed for immersion. Our swimsuits have a specific waterproof membrane that prevents water from getting in and flow from getting out — even in chlorinated pools or the sea.
Chlorinated pool AND sea water — does it work in both?
Yes, both. The technology has been tested in chlorinated and sea water. Chlorine doesn't affect the waterproof membrane or absorption capacity. Neither does salt.
Does it protect against UV rays?
Yes. The outer layer provides UV 50+ protection, shielding skin from harmful rays even when wet.

Care & Durability

How do I care for my swimsuit?
Rinse in cold water straight after use, then machine wash at 30°C with your usual detergent. No fabric softener, no tumble dryer. Air dry — that's it.
How long does it take to dry?
Air-dried, around 4–6 hours depending on the heat. If you're going on holiday, pack two — while one dries, you wear the other.
Does absorption decrease with washing?
No, as long as you follow the care instructions (30°C, no fabric softener, no tumble dryer).
How long does a Sybille swimsuit last?
With proper care, expect 2–5 years depending on frequency of use.
Can I use Marseille soap or vinegar?
Marseille soap is perfect for hand rinsing. Diluted white vinegar can be used occasionally to neutralise residual odours. Avoid bleach and chemical stain removers.

Use

How long can I wear it?
Up to 12 hours depending on flow. You can swim, sunbathe, have lunch, swim again — a full day at the beach or pool without needing to change.
Is there an odour after swimming?
No. The intimate layer has antibacterial treatment to prevent any odour from developing.
From what age can it be worn?
From the very first period. It's often the ideal solution for teenagers: nothing to insert, no stress about leaking during swimming. Sizes from XS (ages 10–14).
Can I wear it as a normal swimsuit outside my period?
Absolutely. It's a real swimsuit first and foremost — stylish, comfortable, thin.
Can I combine it with a cup or tampon?
Yes, and we actually recommend it for heavy flow. The swimsuit acts as a safety net: if the cup overflows or the tampon saturates, the swimsuit takes over.
Can I do water sports in it?
Swimming, aqua aerobics, paddleboarding, snorkelling — no problem. The swimsuit is designed to move with you.
What about light bladder leaks?
The absorbent technology also works for light bladder leaks. Many post-partum or perimenopausal customers use it at the pool for exactly this reason.

Orders & Customer Service

How do I choose my size?
Our swimsuits run slightly small — go one size up from your usual size. A detailed size guide is available on each product page.
Is it really worth the price?
£29.90. Over 5 years, that's about 3p per use — versus 25p for a disposable tampon. Beyond the savings, it's 1,000+ disposables avoided.
What are the delivery times?
Delivery in 5–7 working days to mainland UK. Free shipping on orders over £50. You'll receive a tracking number by email as soon as it ships.
What if it doesn't fit or leaks?
30 days to test it. Wrong size: free exchange. Product doesn't deliver: full refund, even worn, even washed. Zero risk to try.
Is payment secure?
Yes, 100%. We use Shopify Payments' secure payment platform (SSL encryption). Credit card, Apple Pay or Shop Pay.
Can I give a Sybille swimsuit as a gift?
Of course. The exchange is free within 30 days if the recipient needs to swap sizes.