Nylon-spandex blends with a high percentage of nylon hold color best.

Nylon-spandex, with at least 80% nylon.

Polyester is more chlorine-resistant but usually fades and stretches faster than nylon. High-nylon blends absorb less chlorine and keep their dye better over repeated swims. The spandex gives the stretch you need, but the nylon does the heavy lifting for color retention.

Even the best fabric will eventually fade if you’re in a pool every day—chlorine is harsh. But a quality nylon-spandex suit (avoid cheap blends with too much polyester or elastane) will outlast anything else by months.

Rinse it with cold water after every swim, and you’ll get a solid season or two before it starts looking tired.