[Objective] The study aims to explore the growth and physiological response characteristics of Canavalia maritima seedlings under water stress, and provide a reference for water management during the seedling stage and for the cultivation of high-quality plants in coastal sandy lands.[Methods] One-year-old C. maritima seedlings were subjected to simulated drought (soil relative water content at 20%, 40%, and 60%), suitable water content (80%, control), and waterlogging (100%) through a pot water control experiment. Their growth and physiological indices were analyzed. [Results] Under both drought and waterlogging stress, leaf dry weight significantly decreased, while leaf relative water content significantly increased. Seedling height and leaf area significantly increased under waterlogging but significantly decreased under severe drought. Total root length, total root surface area, total root volume, and mean root diameter increased under drought and decreased under waterlogging. The content of malondialdehyde and the activities of catalase (CAT) and peroxidase (POD) significantly increased, while the activity of superoxide dismutase (SOD) remained relatively stable. Soluble protein content decreased, whereas soluble sugar and proline contents significantly increased. The chlorophyll content significantly decreased under severe drought. Initial fluorescence significantly increased, while maximum fluorescence , maximum photochemical efficiency, and maximum quantum yield significantly decreased.[Conclusion] Under drought and waterlogging stress, C. maritima seedlings demonstrated strong tolerance by altering water accumulation and distribution patterns, increasing the activities of CAT and POD, and enhancing soluble sugar and proline contents.