The concept of long-range DAS interrogation utilizing existing telecommunication cables for oceanic monitoring has been successfully demonstrated in several field trials. Real-time monitoring capabilities, low instrument noise, high spatial resolution and extended aperture are beneficial for the development of new DAS applications to observe cetacean and other marine fauna, to monitor marine traffic, to detect earthquakes, tele-seismic events, and microseism signals. Furthermore, DAS interrogation in coexistence with live telecom traffic was validated in high-capacity telecommunication networks. The results show that the DAS measurements are provided within the same range, sensitivity, and high fidelity as with DAS interrogation on dark fibers, importantly without interference to live telecom traffic. These new technology advances allow the full utilization of existing telecommunication infrastructure providing a smart surveillance tool of the oceanic environment. It will be a window opener to less explored areas with sparse data coverage because the infrastructure of submarine fiber optic cables covers nearly all oceans around the globe.