Based on a simple geometrical picture, the effect of a water molecule on the hydrogen bond in its adjacent pair of water molecules is related to the tetrahedral nature of water. The structural aspect of hydrophobic hydration is then treated in terms of the change in the geometry of the local environment of the solvent water due to insertion of a hydrophobic solute. It is shown that the local environment around the hydrophobic solute is favorable for the formation of hydrogen bonds between the neighboring water molecules. The density effect of liquid water is also treated in terms of the geometrical features of the local environment.