Cotton or acrylic blends. Loose stitches will sag.

Stick with a tight stitch pattern and a fiber that doesn’t stretch out when wet. Cotton or a cotton-acrylic blend holds shape way better than pure acrylic or wool. Loose lace or openwork crochet looks great on a hanger but turns into a droopy mess after one swim.

Also: line it. A built-in swimsuit lining or a separate bikini underneath keeps everything in place and prevents the fabric from stretching from the weight of water. If you’re making it yourself, use a smaller hook than the yarn label suggests — that tight tension is your friend.

You’re basically building a net that needs to stay tight. Treat it like a rigid structure, not a cozy sweater.