You are standing at the edge of the pool; the Atlantic breeze is warm; the sun is perfect — and then you remember. Your period started this morning.

For too long, this moment meant one of two things: skipping the swim or reaching for a tampon and hoping for the best. But there is now a third option that is quietly changing the way women experience summer in Portugal and across Europe. It is called menstrual swimwear, and the way it works is more clever than most people expect.

At Maiswim, we designed our leak-proof swimwear from scratch with one promise: you should never have to choose between your period and the ocean. Here is exactly how technology makes that promise possible.

The Problem with Conventional Options

Tampons and menstrual cups work reasonably well on land. In water, however, they become unreliable. Pool chlorine, saltwater, and constant movement can all interfere with their effectiveness. Pads become completely useless the moment they get wet. The result is that millions of women simply avoid swimming during their cycle — not because it is physically necessary, but because the right product did not exist.

That gap is precisely what leak-proof menstrual swimwear was engineered to close.

The Maiswim Technology: A Four-Layer System Built for Water

What looks like a regular bikini bottom or swimsuit on the outside is, in reality, a precisely engineered three-layer structure in the gusset area. Each layer plays a specific role, and together they allow Maiswim pieces to hold up to 18ml of menstrual flow — that is roughly equivalent to two to three regular tampon changes — without leaking, even when you are fully submerged.

Here is what happens at each layer:

Layer 1 — The Inner Absorption Layer

The first layer that your skin contacts is a soft, moisture-wicking fabric designed to draw menstrual fluid away from the body and lock it into the absorbent core. This layer performs two jobs simultaneously: it keeps you feeling dry and comfortable, and it pulls fluid inward, so it cannot travel back out.

Critically, this layer is also breathable and anti-bacterial, which prevents Oduor from developing during wear. Whether you are in the water or lying on a sun lounger, the inner layer maintains a clean, dry feeling against your skin.

Layer 2 — The Absorbent Core

This is where the 18ml capacity lives. The core layer is an ultra-thin but highly absorbent fabric engineered to hold menstrual fluid securely in place. Despite holding a significant volume, it remains thin and discreet — you will not see any bulge or feel any padding through your swimsuit.

This absorbent core is what fundamentally separates Maiswim menstrual swimwear from a regular swimsuit. A conventional bikini bottom has no ability to absorb or contain menstrual flow. Maiswim's core layer does this reliably, even under the dynamic conditions of swimming.

Layer 3 — The Waterproof Barrier

The outermost layer of the gusset construction is a waterproof barrier fabric. This layer does two distinct things that are both essential for swimming:

First, it prevents menstrual fluid from escaping outward into the water. Your flow stays locked inside the garment regardless of how much you move, dive, or splash.

Second, it prevents pool water or seawater from penetrating inward and saturating the absorbent core. This is the detail that most people find surprising. Because the waterproof barrier blocks water from entering, the absorbent core remains dry and fully functional throughout your swim. You are not wasting your swimwear capacity absorbing pool water — it is reserved entirely for your flow.

Layer 4 — Normal Layer

Made from the softest, most breathable materials, this layer is gentle on your skin and designed to prevent irritation or allergies.

Why the 18ml Capacity Matters?

The average menstrual flow across an entire period is roughly 30 to 60ml. On a moderate day, most women experience between 6 and 15ml of flow. Maiswim's 18ml leak-proof capacity comfortably covers moderate flow days when worn alone.

On heavier days, Maiswim swimwear works effectively as a backup layer alongside a menstrual cup or tampon — providing a second line of defence that means a leak at the beach becomes essentially impossible.

This design makes Maiswim genuinely versatile: confident solo wear on light to moderate days, and reliable backup protection on heavier ones.

Made in Portugal, Built for Sustainability

Maiswim is proudly designed and produced in Portugal. Beyond the technology, every piece is also built with a sustainability commitment at its core, making it one of the leading choices for anyone looking for sustainable menstrual swimwear in Portugal.

Each time you choose a Maiswim bikini or swimsuit over disposable period products for a beach day, you are eliminating waste. A single pair of Maiswim swimwear can replace hundreds of single-use products across its lifespan. For women who swim regularly through summer, that adds up to meaningful environmental impact — all without compromising on style, comfort, or protection.

Our swimwear is available in bikini and swimsuit styles, designed to look and feel like premium beachwear — because that is exactly what they are.

The Bottom Line

Menstrual swimwear works because it solves a problem that disposable products were never designed for: keeping you protected in water, comfortably and invisibly. Maiswim's three-layer system — absorption, retention, and waterproof protection — is the reason you can dive into the Atlantic on day two of your period and not give it a second thought.

If you have been looking for the best menstrual swimwear in Portugal that combines real leak-proof performance with eco-conscious design and a style you actually want to wear, Maiswim was built for exactly that.

Explore our full swimwear collection — bikinis and swimsuits — and swim every day of the month.