The maritime sector’s shift toward low-carbon propulsion demands energy carriers with high storage density, safety, and shipboard compatibility. Liquid Organic Hydrogen Carriers (LOHCs) provide a promising option by enabling hydrogen storage in a stable liquid phase under ambient conditions. This work develops the conceptual design and first-principles modelling framework of an LOHC-based hydrogen supply chain for marine applications. The model captures the complete LOHC-to-fuel-cell pathway, including LOHC storage, catalytic dehydrogenation, hydrogen buffering, thermal integration, and fuel-cell utilization. The storage subsystem incorporates thermodynamic properties, mass-flow relations, and tank-volume balances. A core contribution is the theoretical formulation of the dehydrogenation reactor using reaction-order kinetics, Arrhenius temperature dependence, and coupled molar and mass balances. Phase-dependent logic differentiates filling, reaction, and discharge modes. Additional modules include gas-phase buffer-tank thermodynamics, idealized combustion and thermal-loop balances, and an electrochemical fuel-cell model. This modular theoretical framework supports future MBSE development and integration of LOHC-based marine energy systems.