My oldest son, Jack, as I often write, has tried skiing and now wakeboarding and enjoys it immensely. My younger son, Sam, is autistic. He is reasonably high functioning and we don't limit much with him but he usually just sits in the boat, partakes in some discussion when asked questions but generally keeps to himself the whole time. It wouldn't always be his choice to go on the boat but it is ritual now.
Sunday, for some reason, Jack and I were talking smack to Sam about how it was time he try kneeboarding (figured it would be the easiest discipline to get him riding). His responses were not overtly negative so I continued to state it matter of factly that he would be doing it after jack's first run on the wakeboard. He was visibly nervous and some of his autism ticks were in high gear. So when Jack finished up we dropped a kneeboard into the water and got Sam in as well. After explaining how to ride on his stomach at first and how he would get up on his knees we gave it a try. Just in idle mind you, he let out a shriek like bloody murder was happening. So we decided that I would get in the water and steady the kneeboard and get dragged behind until I was convinced he could stay up on his own and then let him go. This would let him start on his knees and not have to transition from laying flat up to being on his knees.
Took a couple of tries to get him to understand to lean against the rope/boat to stay up but he got it. They took a couple laps around this small area of the lake we were in (no boat traffic) and after one lap Sam was ready to join me in the water where he left me but I told the driver to keep going one more lap. He did it and we all praised him wildly. Not sure we'll get him to do it again anytime soon but it was something fun to see. Very proud moment for us.
There is a short excerpt video on the Bluemedia page of Sam taking his first ride on a kneeboard.