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.
Hold a paddle in the hand of your affected arm.
Ask your assistant to stand beside your hip on your unaffected side.
Your assistant can then assist you in rolling onto your side towards your affected arm, using their arms around your hips for support.
Your assistant shall then drag you 180 degrees through the water, leading with your feet, as you allow your arm to stretch out in front of you.