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.
Place an inflatable ring under your unaffected leg and keep your affected leg straight.
Ask your assistant to stand at your feet facing towards you with one of their hands cupping under the heel of your affected leg.
On your assistant's command, bend your knee by pushing your heel towards the floor into your helper’s resistance.
Your assistant will need to adjust their position to accommodate this movement.
Return to the start position and repeat.