The significance of swimming coach's division of students into first, second and third lines lies in distinguishing students' swimming skills and levels. Specifically, first-line athletes are usually students who have reached the standard in provincial, municipal and above official competitions, second-line athletes are students who have reached the standard in municipal and above official competitions, and third-line athletes are students who have reached the standard in district and county official competitions. The main purpose of this division is to better guide students to improve their swimming skills and provide them with corresponding competition opportunities.