Kick like a Duck
When beginners try to kick enthusiastically, they generally use every
part of their body. They flap their arms, shrug their shoulders, grit
their teeth, duck their head, lean backward etc. What they really
need to do is kick like a duck swimming.

Picture a duck swimming along, minding its business. The part of the
duck which you can see, that which is above the water, is perfectly
relaxed and composed, cruising along undisturbed. The picture under
the water is completely different. The duck's legs are churning away,
working up a storm.