The goal of this work has been to create a comprehensive picture of planetary ice shells given the fact that ocean derived ices behave as multiphase reactive porous media. Furthermore, it seeks to assess the implications this has on the geophysics and habitability of ice-ocean worlds such that testable predictions can be made that relate observable features to interior properties and processes. The progressive and multipronged approach taken throughout this work builds from first principles a novel finite difference model of planetary ices which has been validated against both analytical solutions and empirical observations of diverse terrestrial ice-ocean and -brine environments. The model accounts for the multiphase evolution of ice-ocean/brine systems subject to planetary environmental conditions and produces estimates of ice shell physicochemical evolution and material properties. The model has been designed in such a way that it can be easily adapted and tailored to accommodate diverse thermochemical environments and additional physics. Thus, the model provides a flexible and everevolving tool for simulating the two-phase geophysical processes that govern icy satellites. It can provide predictive estimates of ice shell properties useful for the interpretation of upcoming spacecraft observations (i.e. Europa Clipper) and will be able to actively integrate new information and science goals as the mission progresses. Here, an array of work involved in this multi-pronged approach is presented. Simulation of unique Antarctic ice shelf-ocean-sea ice interactions are discussed. Extension of these terrestrial multiphase sea ice models to the Galilean moon Europa is presented and the implications for ice-ocean world geophysics and habitability are investigated. Analytic work exploring the diversity of ice-ocean interactions across different icy world environments is presented. Ongoing analog field work in north central British Columbia investigating the entrainment of salts and biosignatures in unique planetary ices is discussed. Finally, the integration of these components into an improved picture of ice-ocean world dynamics and future work is reviewed.