The up-welling of water provokes turbulences called quicksands. The clay bottom, the clearness of the water and a very low mineral content, give the water a translucent blue aspect. This is why the Fontenils are sometimes wrongfully called “Eaux bleues” (blue waters). Yet, this is the name of the neighbouring mill and its “bassin de la bouture”, which also takes its source in the Beauce water-table. It is carpeted with aquatic grasses which tint it emerald green. Clouds and the sky reflect into it like a mirror, which gives it its second name of “Eaux Bleues.”