Though it was a warm and pleasant winter day in January with +25C in the morning (on the Pacific ocean level at Tehuantepec) when we got to El Sumidero (at about 1000m high) and entered the Canyon surrounded by 1000m cliffs without sun and covered by clouds and in a boat rushing with the speed about 40 km/h I was sorry that I didn't put on a jacket under my PFD.
I thought it would have been funny to get a cold in hot Mexico while everybody feel good in Moscow with its -25C....
I was unpleasantly surprised when I saw a lot of debris floating in the river.
When I came back home I found out that the park borders Tuxtla Gutiérrez, the state’s largest city, which has caused problems with human encroachment and settlement on park land. More importantly, the urban areas and logging areas upstream from the canyon have caused serious pollution problems, with up to 5000 tons of solid waste extracted from the Grijalva River each year.
This waste tend to build up in the canyon because of its narrowness, the convergence of water flows and the presence of the Chicoasén Dam.
Take a personal flotation device or PFD (buoyancy aid or foam core) to keep afloat if a boat turns over. You will be alive for sometime until American crocodiles get sight you, haha!