Women's Rash Guards (Swimwear)

Worn in the water and cut to sit close against the skin, a rash guard takes its name from what surfers get when ribs meet a waxed board deck. Two jobs justify it: stopping that friction, and holding ultraviolet off your back and shoulders for as long as you keep it on.

Tight knits of nylon or polyester with elastane give the stretch. The knit has to be dense enough to stay opaque when soaked and hold its rating wet. A label reading UPF 50 means the fabric lets through roughly one fiftieth of the ultraviolet reaching it, which beats sunscreen for one simple reason. Cloth does not need reapplying every eighty minutes and does not rinse away in the first wave. Seams should be flatlock, sitting level rather than ridged, since a raised seam under the arm rubs through a long session.

Cover-ups work on dry land and come off before you swim. A loose swim tee feels more comfortable but fills with water and balloons, which is what creates drag. Wetsuits use neoprene, a foam rubber, to hold warmth. A rash guard adds almost none of that, so treat it as a sun and friction layer rather than a warmth layer. Within the category, zip fronts go on and off wet far more easily, while pullovers sit flatter under a board or a buoyancy vest.

Snorkelers get the most obvious benefit, since a back floating at the surface burns faster than any other part of the body. Fair skin, children, tropical holidays and any full day on the water all argue for one. Anyone chasing a tan should leave it at home, and heat deserves a thought too, because a close synthetic layer holds a film of warm water against you, welcome at eight in the morning and stifling by a tropical midday.

Hunt the label for an actual UPF number rather than a vague sun claim, then judge the fit standing still. It should feel close to a second skin, since a loose one takes on water and pulls at the shoulders. Thumb holes keep the sleeve down over the wrist, which is where people burn. Sunscreen residue and salt both eat elastane, so run it under cool fresh water right after use, leave out fabric softener and never put it in a dryer.