Swim caps are practical for many reasons.
1. They keep your hair out of your face while you are swimming.
2. They keep your goggles secure and snug.
3. They somewhat protect your hair against chorline, but not completely. They do not keep your hair dry.
4. They are used in open water swimming events and triathlons to easily spot a swimmer and usually written on a bright colored cap is the swimmer's number. Great to have if you are a swimmer in distress! (which hopefully you will never be that swimmer because you have prepared yourself so well!) So, please wear your swim cap.
Here are some tips on how to easily put on a swim cap.