For societies to continue developing economically and maintaining their health, effective management of their water supplies is essential. With uses ranging from desalination and recycling to water treatment and purification, polymers are essential to water science and technology. The application of polymers in water science and technology can have major advantages in terms of cost-effectiveness. For example, the use of polymers as coagulants can reduce the quantity of chemicals needed for treatment, which can reduce operating expenses. Furthermore, the need for additional expensive treatment stages has decreased because the effective removal of impurities from water has been made possible by the development of improved membrane materials. Innovative approaches have been used to create new polymer materials and technologies that might address the challenging problems associated with purifying and treating water. For example, it has been demonstrated that using polymers as coagulants and flocculants increases the effectiveness of the filtration and sedimentation processes. Furthermore, the effective removal of impurities and pollutants from water has been made possible by the development of sophisticated membrane materials. Overall, this chapter examines the creative applications of polymers in water applications, emphasizing how they can increase sustainability, reduce costs, and increase efficacy.