The freestyle kick is at the waist. As the body swings, it drives the legs to draw water. In fact, the state of the legs is naturally relaxed. If stiff, legs are like straight sticks to draw water. Can it have the motivation to move forward? It is true that the instep is straight, but it should be soft. Imagine kicking water with your flippers. Knees are slightly bent from top to bottom. Secondly, the position of the kick should be close to the water surface, and the highest point of the foot is the distance to touch a heel on the water surface. This is the best way to kick, and it also has a splash effect.