Brazilian here. Perfectly safe (color-wise; of course it can be polluted as hell despite its color, just like any other river).
Our ground/mud has a different color. Some areas on the south even have a red soil (very fertile, but makes everything about ground level look dirty very quickly):
https://en.m.wikipedia.org/wiki/Red_soil
There’s great variety of water colors even in the same area, just search for images “meeting of the waters Manaus”:
Brazilian here. Perfectly safe (color-wise; of course it can be polluted as hell despite its color, just like any other river).
Our ground/mud has a different color. Some areas on the south even have a red soil (very fertile, but makes everything about ground level look dirty very quickly): https://en.m.wikipedia.org/wiki/Red_soil
There’s great variety of water colors even in the same area, just search for images “meeting of the waters Manaus”: