With the increasing need for underwater exploration to monitor environment, collect data or recreation, underwater diving and its associated technologies have drawn significant attention. So, a single-electrode triboelectric nanogenerator (STENG) as self-powered wireless sensor based on Maxwell displacement current concept for underwater usages to monitor arterial pulse and body movements of diver is demonstrated. The STENG is fabricated with an optimized 7.5 wt.% of hydrothermally synthesized Ni-MOF and PVDF based composite nanofibers (Ni-MOF/PVDF CNF) on copper foil as electronegative tribo-material and electrospun nylon 66 nanofibers as electropositive tribo-material. The PDMS encapsulation of STENG exhibits water-proof properties with Voc, Isc, and charge output at 45 V, 0.77 µA, and 0.169 µC/cycle, respectively under single-finger tapping. As pulse sensor, STENG monitors arterial pulse and wirelessly transmits information underwater (without external power), wherein STENG generated current creates polarized field in water to get transmitted within a certain distance. Additionally, STENG is demonstrated as a strain sensor to monitor joint movements like ‘elbow, shoulder, knee, etc. Detailed reliability studies reveal that the device is robust against multiple cycles of bending, retains its performance in saline/muddy water, and in the presence of obstacles in the transmission path, which confirms its potential in real life conditions for pulse monitoring of underwater divers. © 2023 Wiley-VCH GmbH.