No, in most cases you should not wear underwear under swim trunks. Swimwear with a mesh liner or a lined pouch already does the job underwear would do, and ordinary underwear soaks up water, sags and takes ages to dry. The one useful exception is unlined trunks, where a swim brief underneath works far better than a pair of everyday boxers.
Why swim trunks are made to be worn on their own
Swim trunks look like shorts, so it is easy to assume they need something underneath. In reality most of them are built as a complete piece. The inner layer is the part that holds everything in place and keeps the outer shorts from clinging when they are wet.
- Mesh liners are sewn into the waistband of classic trunks. They let water drain straight through while giving light support.
- Lined pouches are a second layer of fabric at the front of swim briefs and tight square-leg styles, so nothing shows when the fabric is wet.
- Drawstrings on the waistband mean you can tighten the fit so the whole piece stays put when you dive in.
Our 5-inch swim trunks, for example, are made of 100% polyester, have a breathable mesh liner and an elastic waist with a drawstring. Adding another layer on top of that liner only gets in the way.
What goes wrong with regular underwear under swimwear
If you have ever swum in your boxers under a pair of shorts, you probably already know the answer. Everyday underwear is designed to stay dry, not to spend an hour in a pool.
- It holds water. Cotton in particular stays heavy and wet long after your trunks have dried, which is uncomfortable on the walk back from the beach.
- It sags. A waterlogged pair of boxers pulls down and bunches up around the legs.
- It shows. A longer underwear leg can peek out below shorter trunks, and wet fabric makes lines easier to see.
- Pool water is hard on it. Underwear elastic is not made for regular chlorine, so the waistband wears out faster.
- Some pools do not allow it. Many public pools and spas ask swimmers to wear swimwear only, without everyday clothes underneath.
When a layer underneath does make sense
There are a few situations where wearing something under your trunks is a good idea. In all of them, the right layer is swimwear, not underwear.
- Your trunks have no liner, or you removed it. A swim brief underneath gives the hold that the missing liner used to provide.
- You want more support for water sports such as surfing, paddleboarding or beach volleyball, where loose trunks move around a lot.
- You like the look of swim briefs but want more coverage on the walk to the bar or the boardwalk. Wear the brief to swim and pull trunks on over it afterwards.
A tight swim brief with a lined pouch, such as our printed swim briefs with a double-layer front pouch in chlorine-resistant, quick-dry fabric, works well for this. If you prefer something lighter, the mesh swim briefs have a double-layer contoured pouch and a tag-free finish.
Quick comparison: what to wear under what
| What you are wearing | Anything underneath? | Why |
|---|---|---|
| Swim trunks with mesh liner | No | The liner is the built-in support layer |
| Unlined swim shorts or board shorts | Yes, a swim brief | Adds hold and dries as fast as the shorts |
| Swim briefs | No | They are a single, fitted layer by design |
| Tight square-leg trunks | No | Snug fit plus an inner lining or lined pouch |
| Shorts you also wear in town | Underwear on land, swimwear in the water | Change before you swim, not after |
For a deeper look at the cuts themselves, see our guide to swim trunks vs swim briefs vs board shorts.
Choosing trunks that need nothing extra
If you would rather not think about layers at all, look for these details when you shop for swimwear:
- A built-in liner or lined pouch. This is the single most important feature.
- A snug, adjustable waist. Drawstrings matter more than people think once trunks are wet and heavier.
- Fabric made for water. Polyester or polyamide with spandex sheds water and keeps its shape.
- A fit that matches the activity. Our slim square-leg trunks, in 82% polyamide and 18% spandex with a 3D pouch and a skin-friendly inner lining, stay close to the body for laps and water sports.
The dry-pair plan for after your swim
Underwear still has a role on a beach or pool day: it is what you change into afterwards. Pack one dry pair in a separate pocket of your bag, rinse and towel off, then change before you sit down for lunch or head home. Quick-drying fabrics such as mesh or ice silk feel best if you are still slightly damp. The 5-inch trunks even come with a matching carry pouch, which is handy for keeping the wet pair away from everything else.
Once you are home, rinse your swimwear in cool fresh water and let it dry flat in the shade. Our swimwear care guide covers the rest.
Frequently asked questions
Can I wear boxer briefs under swim trunks?
You can, but it is not a good idea. Boxer briefs soak up water, stay heavy and can show below the trunks. If you want an extra layer, wear a swim brief instead.
Is it okay to cut the mesh liner out of my trunks?
Some men do, usually because the liner feels too tight or too loose. If you remove it, wear a fitted swim brief underneath so you still have support and coverage in the water.
Do you wear anything under swim briefs?
No. Swim briefs are designed as a single layer with a fitted, often lined, pouch. Wearing underwear under them would be visible and uncomfortable.
What should I wear after swimming?
A dry pair of underwear in a breathable fabric. Change as soon as you are out of the water rather than sitting in wet swimwear for hours.
Find swimwear that works on its own
Browse our men's swimwear collection for lined trunks and swim briefs, and pick up a dry pair for later from our men's briefs or best sellers. Every order ships in discreet packaging.
