We present a coarse-grained model for ionic surfactants in explicit aqueous solutions, and study by computer simulation both the impact of water content on the morphology of the system, and the consequent effect of the formed interfaces on the structural features of the absorbed fluid. On increasing the hydration level under ambient conditions, the model exhibits a series of three distinct phases: lamellar, cylindrical and micellar. We characterize the different structures in terms of diffraction patterns and neutron scattering static structure factors. We demonstrate that the rate of variation of the nano-metric sizes of the self-assembled water domains shows peculiar changes in the different phases. We also analyse in depth the structure of the water/confining matrix interfaces, the implications of their tunable degree of curvature, and the properties of water molecules in different restricted environments. Finally, we compare our results with experimental data and their impact on a wide range of important scientific and technological domains, where the behavior of water at the interface with soft materials is crucial.