Ocean wave energy is a promising clean and renewable energy source to mitigate the global energy crisis and environmental issues. Here, a guided-liquid-based isotropic triboelectric–electromagnetic-hybrid nanogenerator (iTEHG) is developed for efficient and sustainable harvesting of omnidirectional ocean wave energy. The fully-enclosed iTEHG is based on a triboelectric nanogenerator (TENG) and electromagnetic generator (EMG), with the structure design of a unique concentric circular electrode pair built on a tilted satellite-dish-inspired plate for gravity-guided motion of the liquid. The newly-designed ocean wave harvester solves the wear and insufficient contact problems of mainstream solid–solid-interfaced TENGs, prolonging the device lifetime, and improves controllability of liquid compared with other solid–liquid-interfaced TENGs. This produces immediate power and current densities of 7.25 µW·cm–3 and 4.85 µA·cm–3 with undifferentiated 360° coverage. The iTEHG can charge a 0.1 F supercapacitor to 3.1 V and continuously drive a wireless thermometer for over 26 min. It exhibits superior performance for practical applications in real ocean environments, proven by continuously driving 320 high luminosity LEDs in Sanya Bay, China, even during quiet periods of ocean activity. The proposed design is expected to have a broad prospect for future blue energy harvesting and inspire development of self-sufficient ocean sensors.