Heat kills swimsuit elastic.

Rinse in cold water after every use and never put it in the dryer.

Swimsuit elastic is basically rubber bands sewn into fabric. Chlorine, salt water, and sunscreen break down the rubber over time. Heat speeds that up dramatically. Hot water washing relaxes the fibers. The dryer bakes them brittle or melts them permanently.

Your move: as soon as you take the suit off, rinse it in cold tap water. No soap needed unless it’s really funky. Let it air dry flat, out of direct sunlight. Never wring it or twist it — that physically stretches the elastic.

If you must wash with detergent, use a gentle one and skip the fabric softener (coats the elastic and ruins its stretch). Hand wash is best, but if you machine wash, put it in a mesh bag on delicate cold cycle.

The biggest mistake people make is tossing a wet swimsuit into a plastic bag or leaving it balled up in the gym locker. Let it dry first.

The elastic will eventually give out no matter what you do. But doing this buys you at least a full extra season.