I tried to teach my Dad fly fishing. His Parkinson's had taken a good grip by then. He was willing to try though. After a day of tuition this was the best he could manage, there was no way I was going to let him loose with a fly attached. I decided that I would cast and he could retrieve, safer for everyone really.
So, given that he was not up to it physically, casting by me was provided and he took the rod from my hand and just concentrated on the retrieve.
Soon he was into a trout, a somewhat emaciated one granted but his first and last fish on the fly.
I wish we had done this years ago he said. The excitement switched his Parkinson's back on and we had to leave before he became immobile. That was the last time I ever went fishing with my Dad.