You can get a swim cap at dicks sporting goods. I have even sometimes seen them at places such as walmart and Kmart. If you want to get a cap online you can go to www.swimoutlet.com Keep in mind, when purchasing a swim cap there are different kinds, latex and silicone. Personally, I think silicone is better because it doesn't hurt your head as much and last longer than the latex. The latex caps are good for a couple times use. Since you said you are a teenage girl you can get a long hair cap, If you have longer hair.