Initially it looked nothing like this to me as I was walking along the river Mayenne in France last week. First of all, when you walk along a road or path you look at the opaque surface in front of you and your eyes adjust to that optically, if you see what I mean. If you then let your eyes move sideways to look at the water, you tend to focus on the surface just like you did on the ground. Sometimes in order to see the reflection you have to refocus, something the brain does somehow, as if there is another layer under the water surface.
Still my eyes could not pick up the vibrant colours like the camera did. Perhaps my eyes are getting old, or it may be that I am just human, but the camera eye is far superior to any human eye. I was very pleased that I interrupted the walk to take this photo once I saw it on the camera display. I was even more surprised when I saw it in full on my computer screen.