|*Hello from Sid and the Critique Club*
Sadly, an undervalued image worthy of a much higher score than it received. It displays good creative vision and your title adds another dimension.
I am unfamiliar with your post-processing technique but I always prefer to do my mono conversion in PS. Whatever your technique is it has made, what I suspect was probably a mediocre mono image from the camera into a much stronger image.
The problem with the in-camera mono option is that it throws all of your valuable colour data away thus severely limiting your options, in particular colour filters, which is where all of your tonal possibilities are held.
The foreground leaf grabs your attention and lets you explore the other underwater debris nearby, your eye is then naturally led up the boulder to those absolutely gorgeous ripples after feasting on those slowly drifting up and out of the top of the image. You have a lovely, near full, range of tones, with detail in all areas from the darkest shadows to the bright highlight of the ripple.
Its sad that it scored so low but how on earth anyone can possibly justify the sub fours is way beyond my comprehension, they have managed to completely distort the end result, you have my sympathy.
More of the same please, Sid