At the mouth of the Zama river we entered into a fluvial network worthy of attention. The Zama, Mataveni, Atabapo, Tuamini, Temi and Guianai rivers have aguas negras, that is, seen as a mass they appear brown like coffee, or greenish-black. These waters are, however, beautifully clear and very tasty. I have observed that crocodiles and mosquitoes, but not the zancudos, tend to avoid the black waters.