The Travel Guide

I came across a story about piranhas a short while ago that, for some reason, caught my attention. I guess its easy to assume I have a rather macabre sense of destiny but the interesting part of the story was not the 38 people who were skeletonized when their bus crashed into the Urubu River, a tributary of the Amazon, but by the definition of the Urubu as a 'black water' river.
Immediately I began to wonder if the little fish, packed with rows of scalpel sharp teeth were the reason the river was described as black. Maybe it was because the people who lived around the area knew that darkness was the only outcome for sweaty travelers taking a quick midnight swim or perhaps they were talking about the hearts of those mighty carnivores who can strip a man's body of flesh in minutes, a reference to their bloodlust and animosity directed towards lumbering land dwellers.
The first definition of 'black water' that I found was in reference to an area off the coast of Florida, where after the ocean's water turned black, the locals complained to the government and everyone shrugged their shoulders until a scientist with a penchant for poop decided that human waste was likely an element in the darkening of the Atlantic. That seemed to fit with other definitions which explained that 'black water' is what can infect otherwise friendly places with parasites and other vermin, another testament to our ingenuity and advanced technology.
I was still unsatisfied, simply because that definition didn't fit with the ad I soon found describing a breathtaking and untouched wilderness that could be found on their 'black water cruise'. The first definition left a lot to be desired as far as a get away from the stench and decrepitude found in the big city.
It took another couple of hits before I found a site that described 'black water' as a river that is unusually pure, devoid of minerals, parasites and other bacteria. The colour of the water comes about after a hard rain when the sediment from the surrounding forests runs into the river, clouding it for hours until everything settles down. To add to the confusion the sight claimed that 'black water rivers' were some of the most pristine in the world, with a clarity that allows for maximum visibility, except, of course, for when its raining.
So, to sum up, a 'black water river, is either one that is polluted with human waste or the most pristine the world has to offer. Makes me want to do a bit more investigating before I head out on vacation. All I have to worry about now is the piranhas.