Swimming Costume Material: What Swimsuits Are Made Of

You've probably bought a swimming costume that turned baggy at the seat after one summer of pool visits. That's a material choice, not a sewing fault.

This guide breaks down swimming costume material in plain language — the fibres, weights and finishes that decide how a costume fits, lasts and protects. We manufacture these fabrics, so the numbers are mill figures, not marketing.

What's Actually in a Swimming Costume

Fibre	Role	Trade-off
Polyester	Structure, chlorine + UV resistance	Firmer hand
Nylon	Softness, quick dry	Weaker chlorine life
Elastane (spandex)	Four-way stretch and recovery	Needs 15-20% for real stretch

The elastane percentage is the number to watch. Below 15% and the recovery sags by the second season — we've dropped those blends from our swim range for exactly that reason.

Polyester or Nylon — How to Choose

One question settles it: pool or beach?

• Pool, competition, swim lessons — polyester-elastane. It shrugs off chlorine and holds shape through hundreds of swims.
• Fashion swim, occasional beach days — nylon-elastane. Softer against the skin, and chlorine matters less when it rarely sees a pool.

We walk through the chlorine side in depth on our chlorine-resistant swimwear fabric page.

Weight, Opacity and Comfort

A costume that turns see-through when wet is a returned costume. Weight is the fix:

• 180-200 GSM for light fashion pieces
• 200-220 GSM for everyday one-pieces
• 220-240 GSM for compressive, fully opaque competition suits

Our core swim fabric is chlorine-resistant, UPF 50+ and four-way stretch — the full build sits on the Swimwear Fabric product page, and the wider sourcing picture is in our swimwear fabric buyer's guide.

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