The purpose of a swim cap is to streamline a swimmer's performance and protect their hair. Swim caps reduce drag in the water, allowing athletes to move more efficiently. They help keep hair out of the face and eyes, which can impede vision and performance. Additionally, caps can create a uniform look for competitive teams, promoting team spirit and identity. Some swim caps are also designed to keep the head warm in cooler water. Overall, suitable swim cap choice can enhance a swimmer's experience and effectiveness in the pool.