The River of Five Colors - In Colombia, Rio Cano Castales, or the ‘river of five colors’, is a special place where for a brief period of time every year when the conditions are just right, the river explodes with vibrant colours your eyes won’t believe. During the short span between the wet and dry season, when the water level is just right, a unique species of plant that lines the river floor called Macarenia clavigera turns a brilliant red. It is offset by splotches of yellow and green sand, blue water, and countless shades in between.
Caño Cristales as it is fondly called is a Colombian river located in the Serrania de la Macarena province of Meta. It's a tributary of the Guayabero River. The river is commonly called the "River of Five Colors" or the "Liquid Rainbow," and is even referred to as the most beautiful river in the world due to its striking colors. The bed of the river from the end of July through November is variously colored yellow, green, blue, black, and especially red, the last caused by Macarenia clavigera plants (family Podostemaceae) on the bottom of the river. It is approximately 100km long and no more than 20 meters wide. The phenomenon can be observed during for a special period of a few weeks from June through to November when the temperature is just right. Traveling to the river is not easy as you must fly to the small town of La Macarena and trek through unmarked trails into the national park from there.

Also known as the River of Five Colors, Caño Cristales is the most spectacular natural wonder in the country. Found in the mountain range of Serranía de la Macarena, the river mesmerizes with amazing colors: vivacious yellow, green, blue, black and red shades quiver from the bottom. The Liquid Rainbow is caused by a unique phenomena: a red plant – Macarenia clavigera – growing in the riverbed. Other colors come from black rocks, green algae, blue water and yellow sand, producing an iridescent effect. The river also features waterfalls, pools and caverns, making it even more dramatic. Furthermore – there are no fish or other creatures, so visitors can enjoy uninterrupted bathing in Caño Cristales.
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If the fish are staying away from the water, why are human beings going in? What exactly are the fish avoiding?