Muddy Water for Pure and Clean Truth

IS IT TRUE THAT IF THE HEAD OR TOP OF THE RIVER OR STREAM IS MUDDY THEN ITS MOST LIKELY THAT THE REST OF THE RIVER OR STREAM WILL NE MUDDY AS WELL? THEN HOW IS IT THAT THE NEO -PLATONIC AND MONOPHONIC CHRISTIAN CREED OF 325 AD CAN BE CLEAN AND PURE? (JRSL)