The Hoëgne near Cascade Leopold II
The typical foam on water as in the Hoëgne is caused by foam-forming elements in the bog water: plant saponins and non-saturated fatty acids. In the turbulence of the river forming this white and greasy feeling foam stains. Many saponins are found in plants of the bacon carrot and foxglove families, in chestnut and maple.
The milky mass that you see here is not coming from this but it is the result of the type of recording!