The driver that took me to the national park recommended me to take path 2 to its very end, and then return on path 3, but not the whole way back to the park entrance. Instead he suggested I should hook on to path 6 where it crossed #3 and take the 6 back to path #2. The reason for this was that were some difficult river passages on path 3.
And sure enough, hardly had I crossed #6 when #3 lead me down to a river, 5-6 metres wide and without any apparent way to cross it. I stood there for 15-20 minutes in undecisiveness; maybe I should take the 6 after all? However, eventually, I found out how to cross the river.
After having crossed the river, the path followed the river just by the waterline. The rivlet ran in a gorge that was fairly deep and where the sun did not really reach, so it was wet and a bit slippery.
The water in the river was not really green, but that is probably some trick of light that fooled the camera.