The eggbeater in artistic swimming
Above the surface, the upper body is straight and vertical. Underwater, the knees are raised quite high and bent. A posture that reminds us of a frog: D
The feet make an inward, circular movement. The left foot moves clockwise and the other foot moves in the opposite direction.
The main difficulty is that the part of your body above the surface must remain stable.
The audience must never see the hard underwater work that the swimmers are doing.