There are several steps to learn this.
1st
Lie down on your belly, hold the noodle with stretched arms in front of you.
Start to move your legs. To do this by bending your knees and your heels towards your
buttocks.
Turn the arch of your feet towards the outside and push your legs sidewards, straighten the legs behind you before you start the movement again.
2nd
To learn how to move your arms get rid of the noodle.
Put your arms straight in front of you. And push the water sideways while bending your
elbows until your shoulders, and start the movement again.