Most people enjoy swimming, especially on a hot summer day.
However, the level of swimming skill varies greatly between recreational and competitive swimmers. Even at the competitive level, some swimmers are faster than others. The difference lies in the ability to use the fundamental principles of fluid dynamics to one's advantage. The same principals which makes the best swimmers so fast are employed by anyone who has ever treaded water. In order to understand how these principals apply, we must first understand the forces acting on a swimmer.