Underwater communication using triboelectric nanogenerators (TENGs) offers key benefits such as independence from external power sources and immunity to water conditions, but faces challenges like short transmission range and single-mode operation. This study presents a flexible, bifunctional Janus film as a high-performance TENG for long-distance underwater signal transmission. The PEDOT:PSS-doped charge-generating layer minimizes charge dissipation, while the PEDOT:PSS and BaTiO₃ enriched charge-trapping layer enhances retention, ensuring robust performance in both contact and non-contact modes. Dual-mode transmission supports underwater tasks such as wireless switching, communication, charging, and gesture recognition with 94.84% accuracy. Remarkably, gesture signals transmitted over 200 m through a water pipe set a record for Maxwell's displacement current-based communication. Additionally, a smart rescue system demonstrates the non-contact mode's ability to self-power SOS signal transmission through water pipes in emergency scenarios, unaffected by water quality or pipe shape. This work expands TENG applications in self-powered, long-range underwater communication.