The powerful jet boats try to be courtious following rules of the river, such as slowing down around other craft to avoid wake.  Most of the time, things are harmonious, but one boat was parked in the wrong spot; right in an approach to rapids.  Rivers must have "no parking" zones as well. 

"That's a bad place to park and he isn't going to like me." explained our pilot, "but I have no choice."  Boats must move fast for hydroplaning through shallow rapids.  This avoids scraping bottom. 

Later in the day, as we were docked at a lodge, a small boat sped past with someone yelling out the window.  I don't even know if it was that same boat.  A phrase like "you mother fucker" could be heard by some passengers.  That screeming was in vane as the caption, who I assume the phrase was intended for, couldn't hear it.  He was on the dock side of the boat unloading luggage.  It was just some yelling in the wind, I guess. 

While most of the trip was as harmonious as magnificant, even this remote river can have "people issues."