You will need an assistant for this exercise.
Lie on your back with a buoyancy collar around your neck and a noodle under your hips.
Ask your assistant to stand at your feet facing towards you with each of their hands cupping your heels.
On your assistant's command, simultaneously bend your knees by pulling your heels towards the floor into your helper’s resistance.
Your assistant will need to adjust their position to accommodate this movement.
Your assistant will then adjust their hand position to hold the front of your ankles.
On your assistant's command, simultaneously straighten your knees by pushing your ankles towards the water surface into your helper’s resistance.
Your assistant will need to adjust their position to accommodate this movement.