Quick answer
If your swim shorts have a built-in liner, wear them on their own—no separate underwear needed. If they are unlined, wear a quick-drying swim brief or box cut underneath. Cotton underwear stays wet, chafes, and defeats the purpose of swimwear.
swim brief
How do you know if your swim shorts have a liner?
Turn the shorts inside out and look at the waistband area. A liner is a second layer of mesh or soft fabric sewn inside, usually with an elasticated leg opening. If you see a loose inner brief or mesh basket, the shorts are lined. If the inside is just the same fabric as the outside, they are unlined. Some shorts have a partial liner that covers only the front; treat those as unlined for practical purposes and add your own support layer.
Can you wear regular underwear under swim shorts?
You can, but you probably shouldn’t. Cotton holds water, becomes heavy, and stays damp long after you leave the pool or sea. That creates friction and can lead to chafing. If you must wear something under unlined shorts, choose a pair made from a quick-drying synthetic or lyocell blend—not everyday cotton briefs. The same logic applies to T-shirts: a cotton tee soaked in salt water will cling and stay wet, while a performance fabric dries faster. For swimwear, the best option is a dedicated swim brief or box cut that is designed to get wet.
What is the difference between a swim brief and a box cut?
A swim brief is a close-fitting, high-cut style with minimal coverage—often called a racing brief or bikini cut. A box cut (sometimes called a square cut or trunk) has a straighter, lower leg and more coverage across the hip. Both are designed to be worn as swimwear, either on their own or under unlined shorts. The choice comes down to how much support and coverage you want. A brief offers maximum freedom of movement and dries quickly; a box cut feels more like a short and can be worn alone if you’re comfortable. Neither is right or wrong—it’s about personal preference and the activity.
Should you wear anything under a swim brief or box cut?
No. Swim briefs and box cuts are designed to be worn directly against the skin. Adding underwear underneath creates extra layers that trap water and slow drying. If you need more support, look for a style with an enhanced pouch or a firmer waistband rather than layering. The same principle applies to men’s swimwear layering in general: each additional layer should have a purpose, and for swimming, less is usually more.
How does men’s swimwear layering work for different activities?
For lap swimming, a brief or jammer alone is standard—shorts add drag. For casual beach or pool time, unlined swim shorts over a quick-drying brief give you coverage and support. For lounging or walking to and from the water, a box cut worn alone can double as a short. If you’re transitioning from swim to street, a pair of lightweight shorts over a swim brief lets you change discreetly. The key is to avoid cotton next to your skin and to choose pieces that dry fast.
What should you look for in a swim short liner?
A good liner is soft, stretchy, and made from a quick-drying fabric. Mesh liners offer breathability but can feel rough; softer knit liners feel better against the skin but may take slightly longer to dry. Look for a liner that has an elasticated leg opening so it stays in place, and check that it doesn’t bunch or twist. If the liner is removable, you can adjust based on the activity. Some men prefer to cut out a liner and wear a separate swim brief for more control over fit and fabric.
Can you wear swim shorts without a liner and no underwear?
Yes, but be aware of the trade-offs. Without a liner or underwear, there’s nothing to hold things in place, and the shorts’ fabric may become clingy when wet. For some, that’s fine for a quick dip; for others, it feels insecure. If you go without, choose shorts with a drawstring waist and a slightly longer inseam for coverage. If you want more support, a swim brief underneath solves the problem without adding bulk.
How do you care for swimwear to keep it fresh?
Rinse your swimwear in cool fresh water immediately after use to remove salt, chlorine, and sunscreen. Avoid wringing or twisting—gently squeeze and lay flat to dry away from direct sun. Never put swimwear in a hot dryer; heat breaks down elastic fibers. If you wear a liner or separate brief, wash it the same way. Rotating between two pairs gives each time to dry fully and extends the life of the fabric.
Swimwear FAQ at a glance
What to wear under lined swim shorts
Nothing. The liner is designed to be worn alone. Adding underwear creates extra layers that hold water. Check the inside of your shorts before you pack.
What to wear under unlined swim shorts
A quick-drying swim brief or box cut. Avoid cotton underwear, which stays wet and can chafe. Choose a synthetic or lyocell blend for fast drying.
Swim brief vs box cut
Briefs offer minimal coverage and maximum freedom; box cuts provide more coverage and a shorts-like feel. Pick based on the activity and how much support you want.
Can you wear regular underwear?
Not recommended. Cotton holds water and can cause friction. If you must, use a quick-dry pair. Invest in one dedicated swim layer instead.
How to care for swimwear
Rinse in cool water after each use, dry flat away from direct heat, and never use a hot dryer. Proper care keeps elasticity and color intact.
Everyday essentials that work under swim shorts
- 6 × Boxer Brief: Made of TencelTM lyocell—a fibre derived from certified renewable wood sources—providing silk-like softness, superior breathability, and natural moisture wicking properties. These properties make it a smart choice for a support layer under unlined swim shorts: it dries faster than cotton and feels smooth against wet skin.
- 12 × Y-Brief: Low waist, signature waistband, enhanced pouch for comfort and fit, no-tag construction. A low waist sits below the waistband of most swim shorts, so it stays hidden, while the pouch adds support without extra bulk.
- 2 × Midweight T-Shirt: 220 gsm https://cdlpmiy.com/products/mens-midweight-t-shirt-black-405dd8c52c042a15c9209fe4-1501530Midweight T-Shirt made of a TencelTM lyocell and pima cotton blend, regular fit, crew neck. A breathable tee that dries faster than all-cotton is useful for covering up after a swim without staying damp.
