Marqus R.
Yelp
Should you be lucky enough to travel the Amazon by boat, as I have, viewing the Meeting of Waters (Encontro das Águas) is an absolute must. It's comprised of the confluence of the Rio Negro which is dark in color from the tannic acids of upstream decaying vegetation and the light brown muddy colored, rich in soil, Amazon River (Solimões River). As the waters differ in specific gravity, they don't mix for around 50 miles. It's amazing to see and something found nowhere else in the world. It's also one of the main tourist attractions of Manaus, Brazil.