The electrolysis of water to produce green hydrogen fuel is pivotal for the transition to renewable energy sources. Predominantly, this process utilizes low-temperature alkaline or proton exchange membrane electrolysers, which require high-purity water, posing challenges for large-scale adoption due to freshwater scarcity. Seawater, comprising 96.5% of Earth's water reserves, presents an almost inexhaustible alternative. However, its complex composition, including various salts and organic compounds, complicates direct electrolysis. Specialized anodes and highly efficient electrocatalysts are essential to prevent corrosion and counteract undesirable chlorine evolution reactions. This study investigates the use of low-saline water from the Baltic Sea for hydrogen production via osmotic desalination and alkaline electrolysis using Life Cycle Assessment, focusing on economic, social, and environmental impacts. Findings indicate that electrodialysis is more energy-efficient compared to reverse osmosis, exhibiting lower environmental impacts across most categories, including global warming potential, ecotoxicity, and eutrophication. Reverse osmosis showed higher impacts, especially in fine particulate matter production and water-related parameters. Despite higher operational costs, integrating seawater desalination presents a promising method for renewable energy storage and hydrogen production. Optimizing electrodialysis could enhance its economic feasibility and performance, supporting sustainable green hydrogen production. Our research underscores the significant potential of seawater desalination coupled with electrolysis for sustainable energy transitions, particularly for regions with abundant seawater access but limited freshwater resources.