Marine nanoscience and nanotechnology have become critical interdisciplinary fields that have the potential to revolutionize our understanding and management of marine ecosystems. This review provides a broad overview of the current advancements, applications, and future prospects of nanoscience and nanotechnology in marine environments. It explores how engineered nanomaterials, with their unique properties at the nanoscale, are being utilized to address pressing challenges in marine pollution, environmental monitoring, energy production, and marine biotechnology. The use of nanoparticles for the cleanup of marine pollutants such heavy metals, hydrocarbons, and plastics is one of the main applications covered. Another is the creation of sophisticated biosensors that can identify toxins and infections in real time. Additionally, it emphasizes how nanotechnology may improve marine renewable energy systems by increasing energy conversion device efficiency and providing corrosion-resistant materials for offshore structures. In addition to environmental and energy-related applications, marine nanoscience holds considerable promise for marine biotechnology, particularly in drug delivery systems, biosensors for disease detection, and marine bio-inspired materials. However, despite these promising advancements, the safe use of nanomaterials in marine environments is a major concern due to potential risks such as nanoparticle toxicity, bioaccumulation in marine organisms, and long-term ecological impacts. It is important to understand the interactions between nanoparticles and marine life to mitigate these risks and ensure the responsible development of nanotechnologies. It highlights key challenges and opportunities in marine nanoscience, including the need for better regulatory frameworks, standardized testing protocols, and further research into the environmental fate and behavior of nanomaterials. By addressing these issues, the field can continue to innovate while ensuring the protection and sustainability of marine ecosystems.