What type of doctor said there was nothing to do? Meds or other treatments can often help one get to a better place with pain. Could you see a pain doctor or have you been to a neurologist?
I am not sure about the drop of the foot. I also am not sure about riding waves with a condition like this. I would not be able to pain wise but even if i could I would not in fear of hurting myself. I know everyone is different in terms of what they do. I would discuss the activity with your doctor. We are all different in terms of what we should do. Have you tried pool therapy since you like water?
Have you had your blood sugar tested? When I hear numb feet etc I think of that.
I am not familiar with your d levels but did your doctor state to take supplements? I do though not rx ones even with normal d levels. I have osteoporsis though.
Sorry I am not more help