Canada's offshore margins, spanning the Pacific, Atlantic, and Arctic, host some of the world's most tectonically active and environmentally significant marine settings, yet their systematic observation still depends on a patchwork of instrumentation, infrastructure, and disciplinary expertise. Cabled observatories, ocean-bottom seismometer (OBS) networks, and emerging autonomous sensing platforms are rapidly expanding what can be measured offshore, creating new opportunities and new challenges for integrating geophysical, hydrological, and biogeochemical observations into a coherent picture of the marine environment, and for sustaining the facilities that make them possible. This session brings together the geophysics, marine sensing, and observatory communities to discuss these advances and identify where closer collaboration can accelerate progress. We invite a broad range of contributions on marine geophysics and marine sensing technologies. This includes studies using Ocean Networks Canada (ONC) cabled observatory data, National Facility for Seismological Investigations (NFSI)OBS deployments, and other marine instrumentation to address questions in offshore tectonics, subduction zone processes, submarine geohazards, seafloor geodesy, and ocean-bottom environmental or biogeochemical monitoring. Bioacoustic, passive acoustic monitoring, and underwater soundscape contributions bridging solid-Earth, oceanographic, and biogeoscience perspectives are welcome, including ecological applications of long-term acoustic observations. Contributions addressing methodological and technological advances in marine sensor design, data telemetry, and autonomous or cabled observing systems are also welcome. By bringing together multi-disciplinary contributions from across Canada, the session aims to foster collaboration between the CGU community and the institutions that operate Canada's offshore observing systems.