GUESSING GAME HERE'S MY GUESS
When fishing the klopping discipline the cat is caught very close to the boat ,average sized cats will do most of the fighting around the boat(in very close proximity to),this mmay make the water very turbulent as you'll agree and may even churn up a lot of debris from the bottom .In the case of a flowing river this debris may float away very quickly but in a small body of static water it may take rather long.
I know that cats can hunt in the dark even ,let alone in dirty water but they may be hesitant to "enter" that particular "debris-patch" to even look for food,if they are in a "clearer" patch of water.
As you will agree the above is all guess-work,and contrary to some aforementioned comments I have caught more than one cat on klop in the exact same spot within minutes of one another(dam and river)I really dont have a cut and dry answer to the question but I am merely throwing in another angle.
Cheers