The mesh lining inside bathing suits serves as built-in underwear, providing support, reducing chafing, and letting water drain quickly so your suit doesn’t get heavy and waterlogged. Nearly all men’s swim trunks and many women’s swimsuit bottoms include some form of interior lining, and mesh is the most common type.
Support and Chafe Prevention
When swim trunks get wet, the outer fabric becomes heavier and clings to skin. Without a liner, that heavy, wet fabric rubs directly against sensitive areas with every step, swim stroke, or jump off a diving board. The mesh acts like a lightweight jock strap or brief, keeping everything in place and creating a barrier between your skin and the rougher outer shell.
This matters more than most people realize. Repeated friction from wet fabric can progress from mild redness to raw, broken skin, and damaged skin is more vulnerable to infections like jock itch. The mesh liner reduces that friction by holding snug against the body while the outer shorts move freely over it.
Drainage and Quick Drying
Mesh is full of tiny perforations that let water flow straight through rather than pooling inside your suit. When you step out of the water, gravity pulls the trapped water down and out through those holes, keeping the suit lightweight almost immediately. A solid fabric liner would absorb and hold water the same way the outer shorts do, essentially doubling the amount of wet material stuck to your body.
The open structure of mesh also increases the surface area exposed to air, which speeds up evaporation. This quick-dry effect isn’t just about comfort. Prolonged dampness against skin creates a warm, moist environment where bacteria thrive, increasing the risk of skin irritation and rashes. The faster your suit dries, the less time your skin spends in that bacterial breeding ground.
Preventing the Suction Effect
There’s another benefit most people don’t think about. When wet outer fabric dries or drains quickly, it can suction tight against your body, creating an unflattering and uncomfortable cling. The mesh liner breaks that seal by allowing air to circulate between your skin and the outer layer. Water drains from both sides of the mesh simultaneously, so the shorts release from your body instead of vacuum-sealing to it.
What Mesh Liners Are Made Of
Most mesh liners are made from polyester or nylon, sometimes blended with a small percentage of spandex for stretch. Polyester is the more durable choice for frequent swimmers because it resists chlorine breakdown better than nylon. If you swim in pools regularly, a polyester-based mesh will hold its shape and structure significantly longer. For saltwater and sun exposure, look for linings labeled as UV and saltwater resistant, since both degrade fabric over time.
Mesh vs. Compression Liners
Traditional mesh liners aren’t the only option anymore. Compression liners, which look and feel like fitted athletic boxer briefs sewn into the shorts, have become increasingly popular. The difference comes down to how you plan to spend your day.
Mesh liners excel at ventilation and drainage. The micro-perforations keep airflow high and weight low, making them ideal for casual pool days where you’re hopping in and out of the water frequently. They dry faster and feel lighter on the body. The tradeoff is that mesh covers a smaller area, and if the fit isn’t precise, it can shift, bunch, or pinch. Mesh also lets sand pass through, which can be a problem at the beach.
Compression liners hug the thighs and adapt to your body’s shape, creating consistent support across a larger surface area. They block sand, reduce inner-thigh friction, and stabilize everything during high-movement activities like beach volleyball, surfing, or running. The light pressure they apply is similar to athletic compression shorts. If you’re planning an active day, compression liners minimize chafing more effectively than mesh. The downside is they retain slightly more heat and don’t drain quite as fast.
When Mesh Liners Cause Problems
For all their benefits, mesh liners aren’t universally comfortable. The net-like texture can itself become a source of irritation for some people, especially during extended wear or repeated friction. Poorly fitting mesh that’s too tight can pinch, while mesh that’s too loose defeats the purpose of support entirely. People with sensitive skin sometimes find that the rough texture of cheaper mesh causes more chafing than it prevents.
If the liner bothers you, you have options. Some swimmers cut the mesh out and wear compression shorts or swim briefs underneath instead. Others switch to trunks with built-in compression liners. Removing the mesh entirely and wearing nothing underneath is also fine for casual swimming, though you lose the support and anti-chafe benefits the liner was designed to provide.