There is a tremendous interest in graphene and graphene-based materials triggered by their exceptional electronic, optical, and mechanical properties. Graphene oxide (GO), an oxidized form of graphene, is one of these materials. The fact that the properties of GO can be tuned by modifying its structure, in terms of the types, ratio, and spatial arrangement of functional groups, opens the door for rational design for a wide spectrum of potential applications, e.g., water remediation, energy-harvesting and -storing devices, electrocatalysis, gas separation, and proton-conducting membranes in fuel cells. The growing number of studies on the structure of and processes at the GO/water interface underlines the importance of understanding the interactions between GO and interfacial water. For example, in contrast to the non-oxidized carbon materials, GO is known to be soluble in water and some other organic solvents. Nevertheless, the dominant interactions in GO solutions and their correlation with the two-dimensional (2D) nature of the GO flakes are not fully understood yet. For instance, Dimiev and co-workers have argued that associating the GO solutions nature and stability with the formal macroscopic parameters is not the appropriate approach to explain the properties of such solutions. Instead, they proposed that GO solutions should be treated as true solutions where the nature of the solution is governed only by the chemical interactions between the solute functional groups and the solvent molecules. In other words, the physicochemical properties of GO solutions can be understood by focusing mainly on the GO/liquid interface. This emphasizes the importance of modeling aqueous GO solutions at the atomic level. Especially, the water transport properties in GO membranes have been of great interest, but the results of the relevant studies, as well as their interpretations, are controversial. Here an important parameter is the inter-layer spacing. Using neutron scattering, Buchsteiner et al. have demonstrated that the inter-layer spacing in multi-layer GO ranges between 7 and 11 Å depending on the humidity level. Talyzin et al. 17 using X-ray diffraction have found that immersion of GO in liquid water increases the inter-layer distance from 8 to 12 Å upon changing the temperature.