Understanding the polymer–water nexus is crucial for assessing its positive and negative environmental impacts, particularly concerning environmental matrices and future sustainability. This chapter explores both the beneficial and detrimental aspects, highlighting the needs of both sides of the concern to define precise boundaries. Considering the importance of these boundaries, the advanced water technology and future directions are crucial to examine the role of polymeric materials in structure, tunability, surface modification, and sustainability. The chapter also focuses on advanced technologies for micro- and nanoplastic control, a key negative aspect of the polymer–water nexus. This includes hydrogel and sponge materials, biopolymer chemistry concepts, microstructure polymer platforms, and the degradation of polymers via catalytic and microbial/genetic methods. Furthermore, the study highlights other advanced technologies, such as membrane-based and solar-based systems, and provides future directions. These directions encompass the standardization of analytical techniques, the development of hybrid polymers, inorganic coexistence within organic cycle circulation, economic integration, smart filtration, real-time sensing, scalability, field validity, and the adaptation of biodegradable polymers. Ultimately, future efforts should prioritize sustainability, avoiding the use of potentially negative materials, even if they presently have positive impacts. Therefore, this chapter is crucial to understand the polymer–water nexus as both sides of the same coin which can help illuminate the path toward defining the boundary between them and direct this relationship toward sustainability and strengthening the bond between polymers and water.