Quick answer

Yes, you should treat gym underwear and pool underwear as two separate jobs. For the gym, choose a breathable, moisture-wicking pair that moves with you and dries quickly. For the pool, wear actual swimwear, not everyday underwear, because swim-specific fabrics handle chlorine and water drag far better. Pack at least one clean dry pair for after your workout or swim.

Why gym sweat and pool water call for different underwear

Sweat during a workout is warm, salty, and produced continuously while you move. Pool water is cooler, chemically treated, and saturates fabric instantly. Everyday cotton underwear absorbs sweat and holds it against your skin, which can feel heavy and cause chafing during repeated movement. The same cotton pair in a pool becomes waterlogged, sags, and dries slowly. Gym underwear needs to manage moisture and friction; pool underwear needs to shed water and resist chlorine. That is why the two situations call for different garments rather than one compromise pair.

What to look for in workout underwear

A good pair for the gym prioritizes breathability, a secure fit that does not ride up, and a fabric blend that pulls moisture away from the body. Look for soft modal cotton or microfiber constructions that feel light and dry faster than standard cotton. The cut matters too: briefs and trunks with a defined pouch or support panel reduce shifting during squats, cycling, or running. Avoid loose boxers with excess fabric, which bunch under athletic shorts. If your workout includes heavy sweating, consider bringing a spare pair to change into afterward so you are not sitting in damp fabric.

Can you wear regular underwear under swim shorts?

You can, but you probably should not. Regular underwear under swim shorts absorbs pool or sea water, becomes heavy, and takes hours to dry. It also adds a layer that can bunch and cause discomfort when wet. Swim shorts are designed to be worn alone, with a liner or close-fitting cut that provides support and minimizes drag. If you feel you need extra support, choose swimwear with a built-in liner or a close-fitting cut rather than layering everyday briefs underneath. Reserve your regular underwear for after you have showered and changed.

How to pack a locker bag for both gym and pool days

Start with a small packing list: one pair of moisture-wicking underwear for the workout, one pair of swim shorts for the pool, and one clean dry pair of everyday underwear for the trip home. Add a plastic bag or wet pouch for the damp items. If you swim first and then lift, change out of your swim shorts and into dry gym underwear before your workout. If you lift first, shower and change into your swim shorts before entering the pool. Keeping the roles separate keeps your gym bag organized and your skin comfortable.

When a single pair can work for both

There is one scenario where a single pair of underwear can serve both: if you are doing a low-intensity activity like walking or light stretching near the pool and not actually swimming. In that case, a quick-drying pair of athletic underwear may be fine. But for any real swimming, sweat-heavy workout, or extended time in chlorinated water, the fabric demands are too different. The honest tradeoff is that no everyday underwear is designed to perform like swimwear in the water, and no swim short is designed to manage heavy sweat during a long gym session. Match the garment to the main activity.

Quick FAQ

Can I wear my gym underwear in the pool?

No. Gym underwear is built to manage sweat, not chlorinated water. It will absorb water, sag, and dry slowly, and chlorine can degrade the fabric over time. Always switch to swimwear for the pool.

What fabric is best for gym underwear?

Look for moisture-wicking blends like microfiber or soft modal cotton. These pull sweat away from the skin and dry faster than standard cotton. Check the label for quick-dry or moisture-wicking claims.

Should I bring extra underwear to the gym?

Yes, pack at least one clean dry pair. After a sweaty workout or a swim, changing into dry underwear helps you avoid discomfort and skin irritation. Add a wet pouch for damp items.

Do swim shorts need underwear underneath?

Most swim shorts are designed to be worn alone, often with a built-in liner. Adding everyday underwear can cause bunching and slow drying. Choose a close-fitting swim short with support instead.

Products that fit these situations

  • Ho1 Mini Briefs HO1 | White 359521-0003: Made from particularly soft modal cotton with the HO1 horizontal opening and excellent support. A solid everyday choice for the gym if you prefer a natural feel and reliable support during moderate workouts.
  • Plume Up Trunk Ho1 Up | Red 402373-4063: Short boxer in plain microfiber fabric with a push-up shape and the iconic HO1 opening. Microfiber dries faster than cotton, making this a practical pick for sweaty gym sessions or travel days.
  • Taormina Swim Shorts | Green Print 403178-P126: Close-fitting swim shorts that hug the body without compressing, minimize drag, and stay in place during swimming and water sports. Designed for the pool or beach, so you can skip wearing everyday underwear underneath and avoid waterlogged fabric.