As intelligent sensors for marine applications rapidly advance, there is a growing emphasis on developing efficient, low-cost, and sustainable power sources to enhance their performance. With the continuous development of triboelectric nanogenerators (TENGs), known for their simple structure and versatile operational modes, these devices exhibit promising technological potential and have garnered extensive attention from a broad spectrum of researchers. The single-electrode mode of TENGs presents an effective means to harness eco-friendly energy sourced from flowing water. In this study, the factors affecting the output performance were investigated using different structures of single-electrode solidliquid TENGs placed in a circulating water tank. In addition, the solid-liquid contact process was numerically simulated using the COMSOL Multiphysics software, and significant potential energy changes were obtained for the solid-liquid contact and liquid flow processes. Finally, the energy generated is collected and converted to power several light-emitting diodes, demonstrating that solid-liquid TENGs can generate effective electrical power in a flowing water environment. Through several experimental investigations, we finally determined that the flow rate of the liquid, the thickness of the friction electrode material, and the contact area have the most significant effect on the output efficiency of TENGs in the form of flowing water, which provides a guide for improving their performance in the future.