Enhancing the output is the most crucial challenge in developing triboelectric nanogenerators (TENGs) as an alternative technology to exploit wave energy, which is more difficult than other application scenarios owing to the full-encapsulation requirement and slow agitation of practical waves. Herein, we developed a symmetrical charge pumping method based on a non-contact TENG, achieving boosted performance in practical slow waves. The method allows for synchronously accumulating positive and negative confinement charges to a high density under the synergistic effect of oil dielectrics. More importantly, we found a new control parameter for device performance, termed as confinement stiffness, which refers to the degree of squeezing out of confined charges under Coulombic reaction force. By enhancing confinement stiffness, the output performance and stability of TENGs can be greatly improved. Moreover, a pre-switching power management circuit is designed, and it solves the inconsistency problem of a traditional circuit with the charge pumping method, reaching an 874.6-fold enhancement in capacitor charging. Moreover, a novel negative power phenomenon is reported. Based on these comprehensive designs, the charge density and power output are greatly boosted, reaching 1.6 mC m−2 and 1.215 W, respectively, under ideal conditions. When tested in a 45-meter-long wave basin, the peak power density can reach 176.15 W m−3 under 1 Hz waves, which sets a new record and is 10.37 times greater than that of the reference device. The work demonstrates comprehensive strategies for boosting TENG performance, which should represent a key step toward efficient blue energy harvesting for self-powered systems and marine clean energy.