We were by Dillon Lake, Colorado last week and watched 3 different people kite snow-boarding on Lake Dillon. The winds were fairly light and shifting. They spent lots of time on their butts, then would be jerked upright for a short run, only to fall back on their backside, waiting for the next gust to lift the kite off the snow. This would be a real pain on a boat, unless you have a nice steady breeze that an ocean might provide.
When we were in Hawaii a couple years ago, we watched a guy trying to get into the water (on his board) while hovering his kite above him. Either a gust came along or he mis-steered the kite, but he was dragged face-down up the beach, through some low brush and into someones back yard.
Maybe the versions for boating will require less skill to use??
Jack