Water is the most common and essential as well as mysterious substance on Earth. Water molecule is astoundingly simple, H 2 O with "hydrogen two parts, oxygen one", but "there is also a third thing, that makes it water, and nobody knows what it is" (D. H. Lawrence). Water exhibits a range of anomalous properties such as being liquid in ambient conditions while other substances of comparable molecular weights are gas. Water becomes less dense upon solidification, exhibits abnormally high specific heat capacity, shows a decrease of viscosity upon compression, and so forth. These anomalies, together with many others, have been a source of scientific curiosity and make water the most studied entity. Nowadays, it is known that the third thing that makes it water is the hydrogen bonding (H-bonding). Yet, puzzling questions remain as why do not other H-bonding molecules such as ammonia (NH 3 ) and hydrogen floride (HF) have similar peculiar properties like water? What makes water unique? We discuss here that the way water constructs its hydrogen-bonded network, other than the H-bonding in general, gives rise to the anomalies of water.