Period Flow Bikini - Sidsel bottom
Period Flow Bikini – Sidsel Bottom is a high-waisted menstrual bikini bottom, sewn in nostalgically wrinkled ECONYL® with a flattering and comfortable fit.
What you can't see is the most important:
At the bottom you'll find our discreet, sewn-in absorbent panel with three layers that protects you in the water – so you can swim without worry.
Mix and match with your favorite bikini top and create your own set.
Why you'll love this style
Why you'll love this style
Who is this style named after?
Who is this style named after?
Material
Material
Washing guide
Washing guide
How does it work?
How does it work?Menstrual swimwear, like Flow menstrual panties, is sewn with a built-in pad, consisting of a minimum of 3 technical layers that direct fluid into the pad, absorb the fluid and ensure that you do not bleed or leak through.
👉 You can read much more about how menstrual swimwear works in the guide here.
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Flow's founder
Relaunch of Period Swimwear 2026
"In 2024, we launched period swimwear for the first time with Cartel, and it was a huge success.
In a month and a half we had sold out, and even though we were able to get a small extra batch, it wasn't enough to meet demand.
Now menstrual swimwear is returning to us - all under our own name, and we have spent two years nerding out fit, materials (we have chosen the best Italian fabrics) - and I have tested function and fit.
I'm not a water dog, but of course the samples I had packed in my suitcase had to stand their test.
They passed the UG. I felt safe, comfortable - and delicious. I am incredibly looking forward to seeing you in your swimsuits on the beach, by the pool, in the gardens."
- Catherine
Want to know more about our menstrual swimwear?
Frequently asked questions
Please wear your regular size in your swimwear.
If you are between two sizes, we would suggest the smaller one, as the fabric can stretch when wet.
The absorbency of menstrual swimwear is light to moderate.
If you are bleeding heavily, we suggest that you combine it with a cup or a disk.
Our swimwear is designed with a built-in, absorbent layer that captures and encapsulates menstrual blood. This layer is combined with a waterproof yet breathable membrane that prevents you from bleeding through while swimming or sunbathing.
The textiles are light and quick-drying, ensuring that you can move freely and feel dry shortly after being in the water.
1. If you have bled in your menstrual swimwear, rinse them in cold water until it runs clear.
2. Protect your swimwear in a laundry bag and wash your panties with similar colors at 30-40 degrees.
Tip: You can wash with our Allergy Certified special detergent Bloody Clean .
3. Dry them inside out on a clothesline - and you're good to go again.
👉 Read our full guide on how to take good care of your swimwear here.
Travel-size laundry detergent?
Menstrual panties
Wellness & care
Sleep, exercise and self-care throughout your cycle. Your body changes throughout the month. So does your energy level.
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