An essential element of the ecosystem is water. Water pollution occurs when harmful chemicals or microorganisms are released into water bodies, which results in the degradation of animal and human’s life quality.The most common cause of water pollution is the direct disposal of industrial and human waste into the surface water. Another reason worth mentioning is the oil spill.Since the dawn of industrialization, numerous factories have been discharging toxic chemical compounds such as metallic sulfides or cyanides. When being introduced into lakes, rivers, and seas, these toxic wastes poison freshwater or saltwater animals and plants, subsequently destroy the ecosystem. Even when the industrial waste is buried in the ground, they can still permeate the soil to pollute the underground water, thus begin the process again. Another cause of water pollution is human waste. Various kinds of pathogenic bacteria live in human feces, and they may cause gastrointestinal infection if they appear in the water supply. Oil spills are also the reason for sea pollution. Most of the marine animals cannot digest oil, or cleanse the spilling oil on their feathers. Therefore, they will die soon unless there are human interventions. The spill also adversely affect seawater, which damages the tourist industry of coastal regions.To summarize, water pollution is mostly the result of oil spills and industrial or human waste disposal. It severely affects the environment and subsequently the life of animals and human.