Aquatic viruses are microscopic infectious agents that inhabit water bodies, including oceans, rivers, and lakes. They can infect a variety of organisms, such as bacteria, algae, and marine animals. These viruses play a crucial role in aquatic ecosystems by influencing nutrient cycling and regulating populations of their host organisms. Many aquatic viruses are specific to their hosts, meaning they can target particular species. For example, phage viruses infect bacteria and can help control harmful bacterial blooms. Understanding aquatic viruses is essential for studying ecosystem health and the impacts of environmental changes on aquatic life.