Standing in front of a mirror with your legs slightly bent, simulate a butterfly arm stroke focusing on the following two points:
To make the exercise more fun, you can alternate performing it with your hands open and your hands clenched to get more proprioceptive feedback
To make the exercise more stimulating and lifelike, you can do it lying on a Swiss ball to engage your core.
To make the exercise trickier, you can use resistance bands while simulating the arm stroke. Using resistance bands means you can perform the exercise either standing or – obviously making it more difficult – on a Swiss ball.
Lying on your back on a bed with your glutes at the edge of the bed, simulate the butterfly leg kick. Make sure you do not bend your knees beyond the edge of the bed (the ideal angle is 30-40°).
To make the exercise more complete, you can perform it lying on one side or with one arm extended alongside your head.
To make the exercise more fun you can kick your feet against a rubber ball attached to your ankles by a rope.