Why Do Swim Trunks Have Mesh Lining? (And Why It Feels Like a Cheese Grater)

Swim trunks have mesh lining, that built-in netting, for three reasons: support, modesty, and quick drying. It was invented so men would stop wearing cotton underwear in the water. That is the whole story. The problem is that mesh is a scratchy net, and a scratchy net pressed against your most sensitive real estate for six hours at the beach behaves less like underwear and more like a cheese grater.

In this article we cover what the netting is actually for, why it hurts, whether you can cut it out, and what to wear instead.

Why do swim trunks have netting in them?

The mesh netting showed up decades ago to solve a real problem. Guys used to swim in cotton underwear beneath their trunks. Cotton soaks up water, gets heavy, dries slowly, and sags like a wet sail. Not great.

Mesh was the fix. It gave you:

• Support. A snug-ish layer that keeps everything roughly in place while you swim.
• Modesty. A second layer so wet trunks don't turn see-through or cling in ways you didn't agree to.
• Fast drying. Mesh is mostly holes, and holes dry fast.

For a quick dip in 1985, that was good enough. The trouble starts when you actually move.

Why does mesh lining chafe so badly?

Because mesh is not fabric in any meaningful sense. It is a stiff, open weave, which means the surface touching your skin is a grid of tiny edges. Dry, you barely notice. Wet, three things gang up on you:

1. Wet friction. Wet skin is fragile skin. Every step rubs the mesh grid against your inner thighs and groin.
2. Salt and sand. Ocean water leaves salt crystals in the weave, and sand loves to hide in there too. Now your liner is a cheese grater with seasoning.
3. Time. A quick swim is fine. A full beach day, a hike back to the car, a game of volleyball, and the mesh has sanded through the top layer of skin. That evening waddle to the shower? That is chafing.

One Reddit user described it as sitting on a cheese grater, and thousands of men nodded quietly in agreement. Odin wept.

Can you cut the mesh lining out of swim trunks?

Yes, and the trunks will survive. Snip close to the seam with scissors and the shorts themselves hold up fine.

But understand the trade you are making. Cutting out the mesh removes the chafing grid, and it also removes:

• All support. You are now free-balling in loose polyester. In the water, things float where they want.
• All modesty. Wet, unlined trunks cling. Everyone at the pool learns more about you than planned.
• The hygiene layer. Trunks without a liner and without underwear means bare skin on outer fabric all day.

Cutting the mesh solves one problem and creates three. It is the Viking move of burning your own ship: bold, but now you are stuck on this island.

What should you wear instead of mesh-lined trunks?

You have three real options, from band-aid to actual fix:

Anti-chafe balm or stick. Rubbing a barrier balm on your thighs works for a few hours, then it sweats and washes off and you must reapply. It treats the symptom, not the cause. Fine for one emergency beach day.

Compression shorts under your trunks. A snug boxer-brief style liner in quick-dry fabric stops the rubbing because the fabric moves against fabric, not skin against mesh. Downside: you are buying and wearing two garments, and if the compression short is cotton you have reinvented the 1950s.

Swim trunks with a built-in compression liner. Same idea, one garment. A soft, stretchy, quick-dry inner short sewn into the trunks. Support without the grid, no bunching, nothing to remember to pack. This is the direction most of the better swimwear has moved in the last few years, and once you try it, mesh feels like a prank.

Mesh liner vs compression liner: side by side

The one thing mesh genuinely had going for it, drying speed, stopped being an advantage years ago. Modern polyester-elastane liners dry just as fast without the grid.

How do you treat chafing if it already happened?

If the damage is done: rinse the area with cool water and mild soap, pat it dry (do not rub, you have suffered enough), and apply a plain healing ointment like petroleum jelly. Skip hot showers for a day or two. If the skin is broken, blistered, or looks infected, see a doctor. The Cleveland Clinic has a solid guide on chafing if you want the full medical rundown.

Then throw out the trunks that did this to you. You owe them nothing.

Frequently asked questions

What is the netting in swim trunks called?

It is called a mesh liner or brief liner. Brands describe it as a support layer, and swimwear listings usually mention it as "mesh lining" in the product details.

Does cutting the netting out ruin swim trunks?

No. Cut close to the seam and the trunks hold up fine. But you lose all support and modesty, so most guys who cut the netting out end up wearing compression shorts underneath anyway.

Should you wear underwear under swim trunks?

Not regular underwear. Cotton soaks up water, stays wet for hours, and causes worse chafing than the mesh did. If you want a layer, make it a quick-dry compression short designed to get wet.

Do all swim trunks have mesh lining?

No. Plenty of trunks now come with soft compression liners instead, and some board shorts come unlined entirely. Check the product description for "compression liner" or "brief liner" before buying.

Why does chafing get worse at the beach than the pool?

Salt and sand. Salt water dries into abrasive crystals in the liner, and sand works its way into the mesh weave. Pool chlorine dries your skin out too, but the beach combo is what really does the damage.

How long does swim trunk chafing take to heal?

Mild chafing usually calms down in 2 to 3 days if you keep the area clean, dry, and friction-free. Broken or blistered skin can take a week or more.