βορβόρῳ δ' ὕδωρ λαμπρὸν μιαίνων οὔποθ' εὑρήσεις ποτόν → once limpid waters are stained with mud, you'll never find a drink
Use P. and V. κατηρεφής (Plato but rare P.), V. πετρηρεφής.