Swimming caps are worn by many people in the pool, and it's mainly to provide a sleeker, more hydrodynamic feel in the water while keeping your hair relatively dry. If you're a competitive swimmer, this can give you the extra few tenths of a second you're looking for. Many competitive swimmers also wear swim goggles to help keep their eyes protected during a long training session. Swim caps also help keep hair contained, and if you're swimming in chlorinated water, a cap can also help keep colored hair protected. If you have longer hair, silicone swim caps have a softer touch and tend to be easier to put on and take off without tugging at your hair. Silicone is also hypoallergenic, allowing use by those with sensitivities. Latex swim caps are a bit stretchier, so they give a snug fit while remaining comfortable.
Bright, vibrant swimming caps are an easy way to add a bit of personality to your swimwear. Pick pink or green swim caps to stand out from the competition as you're racing, or pick a more neutral shade, like black or white, to match your suit or team uniform.