Water is a polar molecule as show in the figure below. The positively charged hydrogen ion on water molecule tends to orient itself toward a negatively charged oxygen molecule of neighboring water molecule. Ice has a highly regular crystalline structure which has maximum number of bonds. Liquid water has less hydrogen bonds which are continually forming and breaking. Each molecule of water has an average of 3.4 bond while ice has 4.
Water is highly cohesive which means it sticks to other water molecules.
The polarity and hydrogen bonding of water makes water an excellent solvent for polar molecules. Water greatly weakens electrostatic forces and hydrogen bonding between polar molecules by competing for their charges. Consider the effect of water on hydrogen bonding between a carbonyl and an amid group as shown below. The hydrogen atoms of water can replace the amid hydrogen group as the hydrogen bonding donors and the oxygen atom of water can replace the carbonyl oxygen as the acceptor. Hence, the a strong hydrogen bond between a CO and an NH group forms only if water is excluded.