Information and knowledge explosions boost the development of telecommunication infrastructures, especially for submarine fiber optic cables. These underwater fibers not only undertake most of the international data transmission on this planet, but also offer new opportunities to study earth science and human marine activities. The emerging technology of integrated sensing and communication is putting this concept into practice. In this article, we present work on coastal event monitoring with photonic integrated sensing and communication technology using submarine telecommunication optical cables. Ocean wave analysis, earthquake detection, and marine ferry monitoring are highlighted for detailed analysis. With the proposed integrated system, we successfully observed ocean waves with different frequencies and velocities, microseisms within 200 km, Mw 4.3 - Mw 6.3 earthquakes in the Far East, and vessel sailing activities. Enabled by the novel integrated technology and mass submarine fiber networks, more research works on photonic integrated sensing and communication systems aiming at ocean science and marine engineering are expected for future insights.