New insight into the electrical properties of liquid water, from a standpoint of the physics of electrolytes, is proposed. The dielectric spectrum of water at frequencies 104–1011 Hz is described by a simple diffusional model taking into account the electrophoretic and relaxation effects inherent in electrolytes. The static dielectric permittivity and microwave absorption are derived from diffusion of Coulomb interacting H3O+ and OH− ions instead of orientational motion of H2O molecules. The drift component of diffusion provides the proton dc-conductivity. Ion concentration is found to be 7 orders of magnitude higher than commonly accepted (∼1% of the total concentration of H2O molecules). The findings refer to the basic properties of water and therefore can be the key to solving the water-related problems.