Was on one of our first float trips thru Boquillas Cnyn, stopped maybe 1/4 mile inside the canyon for some shade and r & r. After a few minutes of dead silence we heard a great splashing, boulders rattling, dog barking, hoofs pounding coming upstream, couldn't see around the canyon wall to tell what was coming so braced ourselves and prepared for the worst. Soon two completely naked young Hispanic men riding bareback and with no halters on their horses came whipping their horses up the river from bank to bank as fast as they could go - how did they keep from crippling the horses? - followed by a small white dog. We were enthralled, these guys could have been Comanche warriors two hundred years ago. They paused long enough to say "buenos dias", then whipped the horses across the river again and splashed around a bend out of sight. The dog tried several times to cross the river but the current kept sweeping it back and it finally gave up and trotted back downstream -- to where, we've always wondered? One instance among many of surreal happenings in the outback....