Triboelectric nanogenerators (TENGs) have emerged as a promising technology for harvesting wave energy and converting it into electrical power. However, the practical application of TENGs in real-world ocean environments has been hindered by a lack of comprehensive data on their hydrodynamic responses and output properties under realistic wave-flow conditions. This gap in the literature has limited our understanding of how to optimize TENG designs for efficient wave energy conversion. In this study, a comprehensive series of experiments were conducted using a large wave-flow flume to investigate the performance of a flower-like TENG (FL-TENG) under various hydrodynamic conditions, including wave height, wave frequency, flow velocity, and structural geometry. The output voltage, motion responses, and cable tension of the FL-TENG were monitored using an electrometer, a machine vision-based displacement measurement system, and tensiometers, respectively. The results show that the relationship between the incident wave-flow area and the FL-TENG's output properties is more complex than a simple “bigger is better” trend. It is also found that the output voltage and hydrodynamic responses of the FL-TENG were positively correlated with the aspect ratio of the rectangular incident wave-flow shape. Importantly, the presence of water flow was observed to significantly inhibit the output properties and hydrodynamic responses of the FL-TENG. These findings provide valuable insights and new design considerations for advancing TENG applications in real-world ocean environments, ultimately contributing to the development of more efficient wave energy conversion technologies.