What Are Swim Trunks? | Shorts Built For The Water

Swim trunks are quick-drying shorts made for swimming and water activities, typically featuring an elastic waistband and mesh lining.

Swim trunks are the casual, go-to option for recreational swimming at the beach, lake, or pool. They are typically made from materials like polyester and cotton, and are designed with comfort and convenience in mind rather than competitive performance. Whether you call them swim trunks, swimming trunks, or swim shorts, they are a staple of warm-weather leisure and water-based relaxation.

Swim Trunks: Not Boardshorts, Not Underwear

The most common confusion is between swim trunks and boardshorts. While both are worn for water activities, they serve different purposes. Boardshorts are designed for performance — think surfing or paddleboarding — and are longer, made of quick-drying technical fabrics, and often have a fixed waistband without an internal liner. Swim trunks, on the other hand, are shorter, more casual, and built for recreational wear.

It is also a mistake to treat swim trunks like underwear. They are your outerwear for the water, not a base layer. They are designed for swimming, but they are also acceptable for a walk along the shore or a casual beachside lunch.

The Classic Features and Materials

Here is what typically defines a standard pair of swim trunks:

• Elastic waistband with a non-structured drawcord for a secure, adjustable fit.
• Open side pockets for carrying small essentials, though they do not usually have secure closures.
• Internal mesh lining for support without needing separate underwear.
• Standard materials like cotton and polyester, which hold up to water but are not built for high-speed swimming.

Most swim trunks are designed for leisure rather than active water sports, since they are not engineered for speed or low drag. For most beach days and pool sessions, that is exactly what you need.

When you are ready to buy, comparing a few well-made options is the best way to find your fit. A curated list of top-rated styles can help you narrow down the choice. See our roundup of the 5 best swim trunks for tested recommendations.

How to Care for Your Swim Trunks

Proper care will make any pair last longer. The essential habit is rinsing your trunks in fresh, clean water after every swim. This simple step removes salt, chlorine, and other chemicals that can slowly weaken the fibers.

The fabric’s biggest enemies are harsh chemicals, machine wringing, and excess heat. Avoid soaking them for long periods, wringing them out, and using bleach. You should also skip the tumble dryer and keep them out of direct sunlight while drying. When you machine wash your trunks, use a gentle cycle at 30°C with a soft spin, and skip any bleaching agents.

Following this routine will keep the fabric and waistband in good shape for many seasons, and it is quick enough to do every time you come out of the water.