Free shipping on orders over £100
Before you go
Everything you might want to know, in one place. Tap a question to see the answer.
Our pieces fit true to size and tops and briefs are sold separately, so you can mix and match. The Size Guide has full bust, waist and hip measurements in inches and centimetres, plus international conversions. If you are between sizes we recommend sizing up.
Our swimwear is made from ECONYL® regenerated nylon and lined with GOTS-certified organic cotton. The finished bikini's themselves do not carry a GOTS certification because we work with small, independent assembly workshops. However, every single bikini is lined with authentically sourced organic cotton fabric purchased from a certified supplier.
UK orders usually arrive within 3–5 business days. Europe typically takes 3–7 business days and the rest of the world 7–14 business days. You will receive tracking as soon as your parcel is on its way.
UK shipping is free on orders over £100 and £4.95 otherwise. International shipping is calculated at checkout.
Yes. You have 14 days from delivery to return an item for a refund, provided it is unworn and the labels and hygiene strip are completely intact. Due to the intimate nature of swimwear, returns that do not meet these hygiene requirements cannot be accepted. A pre-addressed returns label and form are included in your parcel. Please obtain proof of postage with tracking. Refunds are processed back to the original payment method within 15 business days.
For returns outside of the UK please ensure you use a tracked service and keep your proof of postage until your refund is issued. Write "BRITISH RETURNED GOODS" on your parcel, stating zero value for each item. Customs and duty charges may apply if this information is not included and this will be deducted from your refund.
If you would like to exchange an item please place a new order while your refund is being processed.
If you believe your item is faulty please contact us via our email or Instagram.
Rinse in cold fresh water after every swim, hand wash gently and lay flat in the shade to dry. Avoid the washing machine, the tumble dryer and harsh detergents.
Email us at evie@swimwithsirena.com, we will reply to you within 1–2 business days. You can also find us on Instagram at @swimwithsirena.
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Luxury Swimwear
Our Philosophy
100% organic cotton lining.
Crafted from ECONYL® regenerated nylon.
Adjustable ties, shaped to sit beautifully.
Ethically made, with care for you and the planet.
The Collections
Where every collection begins
Born from a love of the ocean, endless summers and feeling beautiful in your own skin. Each SIRÉNA collection captures a different moment and adventure — designed to become part of your summer memories.
I.
The PALMA Collection
Explore the line →II.
The MILA Collection
Explore the line →III.
The SIENNA Collection
Explore the line →Join Our Mailing List
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The Edit
By Style
Three distinct silhouettes, each designed for a different way of wearing the sea.
I.
The PALMA Collection
Easy, sun-worn shapes drawn from the coastline — soft ties, clean lines, made for long days by the water.
Explore →II.
The MILA Collection
Gathered, textured pieces that move with you. Soft on skin, light on the planet.
Explore →III.
The SIENNA Collection
Supportive, sculpted shapes for those who want coverage without compromise.
Explore →SIRÉNA creates beautifully crafted, sustainable swimwear with an exceptional fit — designed to help women feel confident, comfortable and effortlessly elegant. Every piece is thoughtfully made with both style and wellbeing at its core, combining timeless design with conscious craftsmanship.
Crafted from ECONYL® regenerated nylon and lined with certified organic cotton, our swimwear is free from microplastics and toxic, hormone-disrupting chemicals where it matters most. Because true luxury is never just about how something looks — it is about how it is made, how it feels against your skin, and the confidence it gives you every time you wear it.
Sustainability sits at the heart of everything we make. Every SIRÉNA piece is designed to be worn for years, not seasons — considered in its materials, gentle on your skin and kinder to the ocean it was made for.
Our swimwear is crafted from ECONYL® regenerated nylon, a fabric spun from reclaimed fishing nets and other nylon waste recovered from the sea. It performs like the finest virgin nylon, but it takes waste out of the water rather than adding to it.
Every piece is lined with GOTS-certified organic cotton, so there is no plastic against your skin where it matters most. The cotton is grown without synthetic pesticides and certified from field to finished garment.
We produce in small batches, made to order wherever we can, so we are not left with unsold stock. Our packaging is plastic-free and recyclable, and we send nothing out that you cannot put straight into your paper recycling.
We are not perfect, and we would rather be honest about that than claim otherwise. We are working on every part of the process, one step at a time, and we will keep telling you exactly where we are up to.