Consistency in experimental observations, numerical calculations, and theoretical predictions revealed that skins of water and ice share the same attribute of supersolidity that is characterized by the identical H-O vibration frequency of 3450 cm-1 in comparison to the values of 3200/3150 cm-1 for bulk water/ice. Molecular undercoordination and inter-electron-pair repulsion relax the hydrogen bond (O:H-O) asymmetrically and cooperatively in length and energy associated with a dual process of nonbonding electron polarization. This relaxation-polarization process enhances the dipole moment, elasticity, viscosity, thermal stability of these skins with 25% density loss, which is responsible for the hydrophobicity and toughness of water skin and for the slippery of ice.