Do You Wear Underwear With Swim Trunks? (Or Should You Just Go Commando?)

No, you do not wear underwear with swim trunks. Most swim trunks come with a liner sewn inside, and that liner is the underwear. It is built to get wet, dry fast, and hold you in place. Cotton boxers and briefs do none of those things. Wear them under your trunks and you get soggy fabric, chafing, and a waistband everyone at the pool can see.

So yes, going commando in swim trunks is normal, and it is what most men do. The liner is already doing the job.

There are two exceptions. If your trunks are unlined, wear a quick-dry compression short or a swim brief, never cotton. And if you are not going in the water at all, your trunks are just shorts, so normal underwear rules apply.

In this article

• Do you go commando in swim shorts?
• Why shouldn't you wear underwear with swim trunks?
• Is it normal to wear underpants under swimming trunks?
• What are shorts with inner lining called?
• What is the alternative to mesh lining in swim trunks?
• Do men prefer lined or unlined swim trunks?
• Should I wear undies under board shorts?
• When is it OK to wear underwear with swim trunks?
• What should you wear under swim trunks instead?
• FAQ

Do you go commando in swim shorts?

Yes. Going commando in swim shorts is normal, and it is what most men do, as long as the shorts have a liner. The liner replaces your underwear. Adding a second layer does not make you better prepared. It just means more wet fabric to carry around.

"Commando" here means no separate underwear. It does not mean no support. A mesh or compression liner still holds everything where it should be.

So the real question is not whether to go commando. It is whether your liner is any good.

If your trunks are unlined, commando is a different story. Nothing sits between your skin and the outer shell, so seams rub wet skin all day, and wet seams win that fight every time. That is how a good beach day turns into inner thigh chafing by dinner.

Vikings crossed the North Sea in wet wool for weeks at a time. We are fairly confident nobody packed a spare pair of briefs to go underneath.

Why shouldn't you wear underwear with swim trunks?

Four reasons, all of them learned the hard way:

• Cotton and water are enemies. Boxers and briefs are usually cotton. Cotton soaks up water, gets heavy, and stays wet for hours. You will be damp long after everyone else is dry.
• Wet underwear chafes. Wet fabric rubbing wet skin is a friction machine. It grinds your inner thighs and groin with every step down the beach. The Cleveland Clinic puts damp skin and repeated rubbing at the top of the chafing causes list.
• Bacteria love it. A warm, damp cotton layer that never dries is a five star resort for bacteria and fungus. That is how rashes and jock itch start.
• Everyone can see it. Wet trunks cling. The waistband and the outline show through to the whole pool.

Your trunks already come with a layer that handles support and coverage. Adding underwear on top is wearing two hats because you do not trust the first hat.

Is it normal to wear underpants under swimming trunks?

It is common enough that you are not strange for asking, but it is not the norm. Most men wear nothing under lined swimming trunks. The men who do wear something are usually wearing a swim brief or a compression short, not regular underpants.

There are three groups.

Men who wear nothing, because their trunks have a liner. That is the majority.

Men who wear a swim brief or compression short, usually because their trunks are unlined or the liner gave up years ago.

And men who wear cotton boxers. Usually once.

If you have been doing it for years, you are not doing damage. You are just doing extra laundry.

What are shorts with inner lining called?

Shorts with an inner lining are called lined swim trunks, and the inner layer itself is called the liner. On product pages you will see three types named:

• Mesh liner. An open netting brief. The old standard, and the scratchiest.
• Brief liner. A solid fabric brief instead of netting. Softer, slower to dry.
• Compression liner. A stretchy short that hugs the thigh. Most support, least rubbing.

The liner exists to do three jobs: support you in the water, stop wet trunks turning see through, and dry fast.

That is the design. The liner IS the underwear.

What is the alternative to mesh lining in swim trunks?

The main alternative to mesh lining is a compression liner: a soft, stretchy inner short that covers more of the thigh and does not use netting at all. A brief liner in solid fabric is the middle option, and fully unlined trunks are the third.

Ranked for a normal beach day: compression liner first, because it supports and stops thigh on thigh rubbing at the same time. Brief liner second, because it is soft but it does not cover the part of the thigh that actually chafes. Mesh last, because netting plus salt plus sand behaves like sandpaper with ambition.

We wrote a full breakdown of swim trunks with a compression liner, and a separate one on swim trunks without mesh if the netting has to go.

Do men prefer lined or unlined swim trunks?

Most men prefer lined swim trunks, because a liner means you can walk out of the water without a second thought about support or transparency. Preference splits by activity, not by taste: swimmers and casual beachgoers want a liner, while surfers and paddlers often choose unlined board shorts so nothing bunches under a wetsuit.

There is no clean survey number on this, so treat anyone quoting one with suspicion. The argument is almost never lined versus unlined. It is mesh versus everything else.

Nine out of ten arguments about liners turn out to be arguments about one specific bad pair of trunks from 2011.

Should I wear undies under board shorts?

Only if the board shorts are unlined, and only if the undies are quick drying. Most board shorts come unlined, which is exactly when a layer makes sense. Reach for a compression short or a swim brief. Never cotton.

The material rule is simple. Whatever touches your skin in the water should be polyester, nylon, or a nylon spandex blend. Those shed water in minutes and slide against your trunks instead of gripping your skin. Cotton drinks water, stays heavy, and turns any layer into a wet rag.

Quick test before you pack: read the tag. If it says cotton, it does not belong in the water.

If your board shorts do have a liner, skip the extra layer entirely.

When is it OK to wear underwear with swim trunks?

There are three honest exceptions.

1. You are not going in the water. Manning the grill? Playing beach volleyball? Just there for the sandwiches? Then your trunks are shorts, and normal underwear rules apply.
2. Your trunks have no liner. Wear something, but make it a quick dry compression short or swim brief.
3. You need more support than the liner gives. Loose mesh liners offer roughly the support of a screen door. If you are running, swimming hard, or playing sport in the water, a proper swim brief or compression short underneath is a fair fix.

Notice the pattern. Even the exceptions call for swim specific layers, not the boxers from your dresser.

What should you wear under swim trunks instead?

If you keep wanting a layer under your trunks, that is not a you problem. That is a trunks problem. Trunks with a soft built-in compression liner remove the whole question: support, coverage, and quick drying in one garment, with no extra underwear in the beach bag.

Frequently asked questions

What do boys wear under their swim trunks?

Nothing, if the trunks have a built-in liner. The liner replaces underwear for kids the same way it does for adults. If a child needs an extra layer for comfort, use a swim specific brief or compression short, because wet cotton chafes children faster than adults.

Do you go commando in swim shorts?

Yes, and it is the normal choice. Lined swim shorts are made to be worn with nothing underneath, since the liner provides support and coverage. Only unlined shorts call for a layer, and it should be a quick drying one.

Do male swimmers wear underwear?

No. Competitive swimmers wear a jammer, brief, or racing suit with nothing underneath, because any extra layer adds drag and holds water. The suit itself is the only layer.

Are you supposed to wear underwear under shorts?

Under regular dry land shorts, yes, unless the shorts have a built-in liner such as running or gym shorts. Under swim trunks, no, because the liner already does that job.

Can you wear boxers as swim trunks?

You can, but they are not made for it. Cotton boxers become heavy and see through in water and take hours to dry, and many public pools ban them outright for hygiene reasons.

Why does my liner feel so uncomfortable?

Because most trunks still use mesh netting, an open weave that traps sand and rubs wet skin raw. Read our full breakdown of why swim trunks have that netting and what to look for instead.