Bungee horses

I was with a group of people in the woods, near a medium-sized pond or reservoir. Next to the water was a framework tower, maybe three or four stories high. Two people from our group were playing a weird sport where they each were mounted on a horse, and around each horse's midsection was tied a bungee cord. Both horses, with the guys on them, were dangling from the tower over the water, slowly bouncing up and down (it was a rather springy cord) and swaying back and forth. The idea was to knock your opponent off his horse, and the two came close to each other a few times and scuffled. I can't say I recall either one falling in the water.