This study provides a critical synthesis of micro- and macroplastic contamination across India’s freshwater and coastal aquatic ecosystems, combining a qualitative literature review with a quantitative comparison of plastic abundance, polymer composition, and pollution/hazard indices from studies spanning 2016–2026. Drawing on published research on Indian rivers, lakes, and coastal waters, the paper identifies fibres and fragments as the most prevalent microplastic types nationally, with macroplastic debris implicated as a major source of secondary microplastic generation and natural sediment functioning as their principal long-term reservoir. The synthesis reveals substantial discrepancies in polymer abundance, particle size, and isolation procedures across studies, complicating direct quantitative comparison, and finds that hazard indices frequently diverge from pollution indices due to variation in polymer-type abundance across datasets. The review concludes by identifying key research gaps — including plastic source apportionment, monsoon-driven transport effects, macroplastic fragmentation dynamics, methodological standardization, and human health impact assessment — that currently limit a unified understanding of plastic pollution in India’s aquatic environments.