Submarine groundwater discharge (SGD) is a crucial process linking terrestrial and marine environments, influencing coastal ecosystems, nutrient cycling, and water quality. Despite its importance, the long-term impacts of future sea-level rise and tidal amplitude changes on SGD remain poorly understood. This study employs a variable-density groundwater flow model to assess the effects of sea-level rise and tidal amplitude variations on both fresh and saline SGD in coastal aquifers. Through a comprehensive sensitivity analysis, we explore the impact of key hydrogeological parameters, including hydraulic conductivity, dispersivity, beach slope, and inland groundwater level or discharge. Our results indicate that saline SGD increases with increasing sea level and tidal amplitude, and that variations in tidal amplitude alone result in larger changes in nearshore saltwater SGD than sea level rise alone, which deserves more attention. Under constant head inland boundary conditions, both sea level rise and tidal amplitude amplification lead to a decrease in fresh SGD. These findings highlight the need to incorporate future sea-level rise and tidal amplitude changes in long-term SGD predictions, with significant implications for coastal water quality and ecosystem management.