<p>This study describes a holistic modeling framework to examine the system performance and techno-economic behavior of marine renewable energy-driven green hydrogen production under operational uncertainty. Moving beyond deterministic assumptions, the framework clearly incorporates operational, environmental, and technological fragilities inherent to marine energy conversion systems. The green hydrogen pathway is modeled in four stages—electricity generation, water treatment, PEM electrolysis, and hydrogen storage—in which the dominant fragility mechanisms are identified and represented. Availability losses, degradation effects, yield variability, and cost uncertainties are propagated throughout the entire conversion chain via Monte Carlo-based stochastic simulations, enabling assessment of lower-tail production risks and cost variability. The framework is demonstrated for a planned green hydrogen facility at the Kilitbahir Strait. Deterministic modeling predicts approximately 12.0 GWh/year of electricity generation with an electricity cost of 116–117 USD/MWh. Under stochastic fragility effects, the mean annual electricity generation decreases to 11.77 GWh/year, the LCOE increases to 128.40 USD/MWh, and the low-tail VaR indicates a possible decline in annual generation to 10.81 GWh/year. Unit water costs range from 2.0301 to 3.5824 USD/m³, while hydrogen production reaches approximately 94 tons/year at a unit cost of 12.2739 USD/kg. Storage and compressor-related fragilities increase the total hydrogen cost to 12.949 USD/kg, highlighting the system-level cumulative effect of operational fragilities at the system level.</p> Graphical Abstract <p>The graphical abstract presents the main stages of the proposed marine current-based green hydrogen production framework, including electricity generation, seawater treatment, PEM electrolysis, and hydrogen storage. It also highlights how operational fragilities propagate through the system and influence final energy and hydrogen costs.</p>