Ski joring, aka horse-pulled skiing, is done on snow, not water, but it is for real: http://www.youtube.com/watch?v=nNZL0Ma7GEs&feature=related
On Bike Polo: What Is Next, Horse Waterskiing?
Ski joring, aka horse-pulled skiing, is done on snow, not water, but it is for real: http://www.youtube.com/watch?v=nNZL0Ma7GEs&feature=related