Triboelectric nanogenerators (TENG) have been proposed as the most promising technology to harvest water wave energy, i.e., the so-called blue energy. Dielectric polymers are typically required for TENG to create static charges, which, however, may produce plastic litters to the ocean after its service. In this work, seawater degradable dielectric polymers are investigated for the applications in TENGs. A promising polymer blend (noted as PLA/PLGA), consisted from seawater-degradation-favorable poly(lactic-co-glycolic acid) (PLGA) and nonseawater-degradable polylatic acid (PLA), shows a mild rate degradation in seawater and complete weight loss within 9 months. Furthermore, the PLA/PLGA is found to be tribo-positive with excellent electrification properties, and is mechanically robust. Then, a hollow-plate-shaped seawater degradable TENG (SD-TENG) is designed using PLA/PLGA as the electrification layer and Mg as the electrode, which demonstrates the ability to convert water wave vibration energy into electricity. This SD-TENG demonstrates a clean approach to exploit the ocean wave energy, and may supply power for future temporary marine instruments without maintenances and environmental damages.