Emergent water pollution accidents range primarily based on pollution location, sources of pollution, levels of pollution, and pollution timeframe. Because of climatic conditions, human factors, and technological flaws, inappropriate chemical usage, spills and explosions in the chemical industry, and oil tankers, there have been significant economic losses, environmental devastation, and deaths. In this paper possible changes that would occur in the ecosystem of a coastal in response to a terrorist attack or/and industrial accident will be identified and discussed. A very brief revision will be done on ecosystem organization, succession, effects of pollutants and biomagnification, and coastal water renewal characteristics to draw possible scenario under a terrorist attack or/and industrial accident. Simple computational models will be used to simulate a coastal ecosystem and demonstrate the possible consequences of an incident.