The widespread usage of nanotechnology in many essential products has raised concerns about the possible release of nanoparticles (NPs) into aquatic habitats. Cerium dioxide (CeO₂) has gained the most interest in the worldwide nanotechnology industry of all types of Ce minerals owing to its beneficial uses in a wide range of industry practices such as catalysts, sunscreens, fuel additives, fuel cells, and biomedicine. Besides, it was realized that CeO₂ nanoparticles (n-CeO₂) have multi-enzyme synthesized properties that create various biological impacts, such as effectively antioxidant towards almost all irritant intracellular reactive oxygen species. Lately, it was discovered that a large amount of n-CeO₂ from untreated industrial waste could be released into the aquatic environment and affect all living organisms. In addition, the physical/chemical characteristics, fate, and bioavailability of nanomaterials in the aquatic environment were discovered to be related to the synthesis technique. Thus, there are intended needs in identifying the optimal technique of synthesized CeO₂ nanoparticles in order to assess their beneficial use or their potential ecotoxicological impacts on aquatic organisms and humans. Therefore, this review sheds light on the possible threats of n-CeO₂ to aquatic creatures as well as its synthesized techniques. Also, it discusses the possible mechanism of n-CeO₂ toxicity as well as their potential benefits in the aquaculture industry.