Ocean waves represent a vast, untapped source of renewable energy, yet current wave energy harvesting technologies often struggle with efficiency, cost, and scale. Triboelectric nanogenerators (TENGs) have emerged as promising devices for mechanical energy harvesting, but their application in wave energy conversion remains limited by challenges in their design and performance. Here, we present a novel swing-arm triboelectric nanogenerator (SA-TENG) specifically designed for wave energy harvesting. Our device employs a pendulum-inspired mechanism with PTFE rollers and nylon tracks, enabling efficient energy capture from the primary motion direction of waves. We developed a dynamic model to characterize the SA-TENG’s motion under wave excitation, providing crucial insights into its operational behavior. Through systematic experimentation and optimization, we achieved a maximum open-circuit voltage of 140 V and a short-circuit current of 1.2 μA. The SA-TENG demonstrated its practical applicability by powering 50 LEDs and operating a humidity–temperature sensor in a self-powered system. This work not only introduces an innovative wave energy harvesting device but also provides a comprehensive framework for modeling and optimizing TENG performance in marine environments. The SA-TENG’s design principles and analysis methods pave the way for scaling up wave energy harvesting, potentially revolutionizing blue energy utilization and contributing to sustainable coastal and maritime technologies.