Swim trunks with liner: what water does to a short, and what the pool asks

A swim trunk without a liner is just a short that gets wet.

Two pairs look the same on a sun lounger by the hotel pool. You only see the difference when someone climbs the ladder out of the water: wet fabric turns heavy and goes looking for skin. What sits underneath decides whether the trunk still looks like a trunk afterwards, or like something you wish you had taken off.

If you know American trunks, you know the idea: a brief sewn into the shorts. The cross-section below puts three trunks side by side while the water rises, and each one does one thing. Their numbers are also the first three chapters of this article: 1 no liner, 2 mesh, 3 elastic. A fourth kind, the compression liner, sits in the table further down.

Do swim trunks need a liner? What public pools ask

It depends on the pool, and the rules can point in opposite directions. New York City requires a mesh lining in men's suits, so trunks without one (1) are the problem there. In a pool in Belfort, France, the short itself is the problem.

The pool rules of NYC Parks say that men's bathing suits must have a mesh lining, and the department's page for outdoor pools adds that staff may check the shorts for one when they cannot tell whether a bathing suit is being worn. Where a lining is required, a trunk with a liner (2 or 3) is the safe choice. Whether a given lining passes is for the lifeguard to decide, so ask at the desk if you are unsure.

Holiday abroad, then, is where it gets strict. The rules of the Belfort pools (July 2026) make a maillot de bain and a swim cap compulsory and say two words about shorts. A swimsuit that may not be a short is in practice swim briefs or tight jammers, so pack those, and a cap, if you want to try a French piscine municipale. Trunks are for the coast and the hotel, and that is where numbers 2 and 3 come in. Every Sanwin Beachwear short has its liner built in.

Is a mesh liner comfortable? Who it suits

It suits the man who walks from the pool straight to a table. The net is open and does not close round your leg, so the short hangs like a pair of chino shorts.

The Tampa is built for that moment. It has a tailored cut, closes with a zip and two adjustable buckles, has a zipped back pocket, and the mesh is attached to the inside.

At a hotel pool you wear it from breakfast to lunch, dive after dive. The peach polyester is tested in chlorine, and between two dives you walk to the terrace without changing.

Every colour of this model is on the Tampa swim shorts page. Why the fabric dries so quickly between dives is in the piece on quick-dry swim trunks.

The drawback of mesh is the size. In a short that is too loose, the edge of the net swings back and forth along the inside of your thigh, and with wet sand that chafes. The Tampa is sized in inches, like jeans, so a US reader can start from the waist size on their jeans label. The buckles take the band in, but the leg openings stay as wide as they are: a size too big is fixed at the waist, not along the leg. Measure a short that fits you well and compare it with the swim trunks size chart.

Are elastic leg openings better than mesh for walking?

For a day on your feet, yes. The elastic closes the liner round your upper leg, so the underlayer stays where it is when the outer fabric gets wet and heavy.

That liner is in the Venice, with a print, and in the plain Miami, both with a classic fit. These shorts have elastic twice, and it helps to keep the two apart. The elastic round each leg belongs to the liner. The waist closes with an elastic band and a luxurious drawcord, where the Tampa has a zip and buckles.

From the water to the bar, along the tideline to the next beach: on a travel day you walk miles in wet trunks, and that is what the elastic round the leg is for. The drawback is the elastic too: too tight, it pinches and leaves a red line. With these shorts that is the mistake we see most. Of the 71 customers and shops who wrote to us about size, 48 found their short too small and 4 too big. In July 2025 a customer in Belgium wrote that his Miami was "a size too small" and asked for his next Venice and Miami in XL. The liner fits as well as the short it hangs in. The Venice and Miami are sized in letters from S to XXL, and you find them on the Venice swim shorts and Miami swim shorts pages.

Mesh or elastic: how to try it on at home

• Put them on bare, with no underwear: that is how you will wear them.
• Squat deep and stand up again. Neither mesh nor elastic should pull anywhere in your groin.
• Take a big step, as onto the ladder of a boat, and feel where the edge runs along your thigh.
• Leave elastic leg openings on for a few minutes. If there is a red line afterwards, take the bigger size.
• Keep the tags on and stay out of the water for now. That way you can swap for another size, free, for a good three months.

From our .com shop, delivery takes 3 to 7 working days in Europe and 6 to 14 in the United States and Canada, and an order placed before 14:00 on a working day ships the same day. Plan the try-on before the trip, not at the airport, and then pack with the beach vacation packing list.

Which liner is right for you?

Choose by what you do after swimming. Walking on to a table asks for mesh, walking and moving asks for elastic, and sport asks for compression.

No liner only makes sense when the short is not your swimwear: over swim briefs for lengths in a strict pool, or aboard a boat over your swimwear. Then a second underlayer is one too many. All models with a liner are together under men's swim shorts.

Chafing, cutting out the mesh, compression: five questions