This summer I had the privilege of paddling with a fellow that is a c5-6 quadriplegic. It was a 2 hour parent + kid class and he was there along with his wife and daughter. I surely learned more that day from that family than they did for me. I look forward to continuing that learning for both of us and hope that we get to paddle together again.
He had a kayak that was adapted with a seat and outriggers much like the one that is shown in this video. In addition, he had special connectors that connected his hands (wrists, actually) to the paddle. He mentioned that the new connectors he was using were a great improvement over what he used to do, which was to duct tape his hands to the paddle.
The video, featuring a paraplegic paddler and his adapted cedar-strip kayak is very inspiring.