Applying an electric field is a well-established experimental method to tune surface wettability. As accessible experimental length scales become shorter, the modification of interfacial properties of water using electric field must come to grips with novel effects existing at the nanoscale. We survey recent progress in understanding these effects on water interfacial tension and on water-mediated interactions using molecular simulations. We highlight the key role of external conditions in determining the system's response to applied electric field. We further discuss the role of appropriate boundary conditions in modeling polar fluids subject to collective polarization. The work reviewed here broadens the basic understanding of applied and internal field effects that can operate in condensed phase systems, from modulating local hydrophilicity/hydrophobicity of engineered and biological surfaces, to surface manipulation in nanofluidic devices.