One Piece n°1 - Forest Green

$118.00 USD


The star piece of the eco-friendly collection, the One-piece with the slit back.

The cut 

  • Its suggestive cut-out on the side does not exclude a pleasantsupport and provides a real freedom of movement.
  • The swimsuit is lined with our softest material.
  • Adjustable straps that attach in 3 ways by a system of Italian-style knots: straight, crossed behind the back or behind the neck.
  • No iron or plastic (let's avoid micro-waste) to adjust the straps but knots. The knots are small and pleasant to wear. On the adjustment side, the iron eyelets slide very poorly on swimsuit materials and tend to loosen the straps too quickly; on the contrary, the knots do not loosen when you are moving.

All our models have been tested by excellent swimmers and water sports aficionadas, in the south of France or during their travels abroad. With this one you can do whatever you want! Cross it in the back to take waves: it will not move.

Size advice  
To choose your size of One-piece, refer to your size of Bottom. For example, if you are a size 36 in panties, you should choose a size S in One-piece. The straps are adjustable and will fit your top.
This swimming costume fits true to size. If you are over 1m70 and not sure which size to choose, go up a size.

If you have any doubts or questions about the size, please contact us at

Our models 
Aude Jane is 1m70, a B cup and wears a size S (36 in Bottom).
Sigrid is 1m65, is a D cup and wears L (40 in Bottom).

Fabric & Care

Posidonia's objective is to use a fabric that contributes to cleaning the oceans and the environment, but also very elegant and comfortable to free women from any constraint of movement. An eco-responsible jersey is also a sustainable jersey, which is why I have chosen the highest range of European fabric made up of waste such as fishing nets and plastic bottles.

78% Recycled Polyamide. 22% Elastane.
Weight: 190gr.
UPF 50 (sun protection).
Bi-directional stretch (marries muscles & movements: great sensation)
Label: OEKO-TEX Standard 100.
Italian fabrics.

🌞 UV protection SPF50


The sea and the salt do not alter your swimsuits if you rinse them with fresh water after each use. Let it dry flat or laid out on its own.

Hand wash your swimsuit. You can wash it in the washing machine at the end of your vacation, on a delicate cycle (max. 30 degrees), with a non-detergent detergent, without spinning or drying cycle.

The chlorine resistance index of our materials is very good. The colors, however, are more delicate.

Customer Reviews

Based on 4 reviews
Anne Lesné
Très satisfaite

Je me suis trompée dans ma commande. Le super service client a été très réactif en annulant ma commande erronée pour que je puisse passer la bonne avec un code de bienvenue pour une remise de 10%. Le maillot est arrivé rapidement, avec un un sac en filet. La qualité semble très élevée, avec un doublage qui permettra de maintenir le tissu dans la durée. Très belle couleur. Les attaches sont réglables.

Elise Pouchelet
Superbe maillot n°1 🌊🩱

Très joli maillot une pièce à la taille adaptative, avec des attaches discrètes et pas du tout gênantes (contrairement à ce que je pensais !). La couleur Vert forêt est aussi superbe. Merci pour ce maillot aux matières recyclées 😍

Apolline CADET


Anne-Claire Cor
Brin de mer

Maillot très bien coupé, correspond à la taille annoncée. Correspond à mes attentes, coloris réussi et tt l’esprit Posidonie réuni dans un vêtement dont j’ai hâte de profiter !!
Bravo à tte l’équipe et à ces efforts pour faire des vêtements comme on les aime.