I made the mistake of calling the horse in the most recent post a polo pony, but Martina pointed out that he is actually a pato horse. I linked to this video in the comments, but I thought I would put it here so it gets seen. (I am not sure the comments come through for those that are subscribed to the blog, especially if they are made later.)
It is certain a sport for the brave… and the young! I fear I have hit the age where a peaceful trail ride without stirrups is about as daring as I get.
Martina has more pictures of the sport here.