Swim caps are more than a style statement--they also protect your hair from the worst of exposure to pool chemicals and keep your hair from tangling in a pool filter or interfering with other swimmers. The fact that swim caps are one-size-fits-all eliminates the worry of sizing when you compare caps; the only considerations that remain are material, fit (only of real concern if you have long hair) and style.
Study the advantages of different swim cap materials. Latex is inexpensive and waterproof, but can’t be worn by those with latex allergies. Silicone caps are also waterproof and very durable, and can be worn by people with latex allergies, but also cost more. Swimmers with long hair or particularly large heads may find that silicone caps tend to slip off easily; they’re best suited to swimmers with short hair. Lycra and polyester swim caps are inexpensive and very lightweight, but porous; unlike latex and silicone caps, Lycra and polyester caps allow your hair to get wet.
Compare fits. All swimming caps come in one size, as they’re elastic enough to stretch to fit almost any head--but you will find caps divided into junior (for children) or senior (for adult) models. Some caps may also be labeled as “high volume,” which means they’re intended for those with larger heads or long hair.
Try on the caps, if necessary, to make sure they have enough room for your hair. Stretch the cap apart with your hands, bend down to the cap, and pull it on over your head from front to back. Pause partway through to bundle your hair into the cap if you have long hair. If the cap seals firm to your skin all the way around your face and neck, even when you twist your head, it has enough volume for your hair.
Compare styles. If ear protection is important to you, some swim caps feature ear pockets that cover your ears completely and also help keep the swim cap from slipping off. You may have to choose a particular color to match caps with other swimmers on your team, but if the choice of color and pattern is up to you, you’ll find the silicone caps in particular tend to come in a wide variety of bright choices.