Aquatic organisms are living beings that thrive in water environments, including oceans, rivers, and lakes. Examples include fish, crustaceans, and mollusks. Fish, such as salmon and tuna, breathe through gills and are often found in schools. Crustaceans, like crabs and shrimp, have hard exoskeletons and play important roles in aquatic ecosystems. Mollusks, which include snails and octopuses, are known for their soft bodies and, in some cases, hard shells. These organisms contribute to the food web and are vital for nutrient cycling in their habitats. Each group has unique adaptations that help them survive in their specific aquatic environments.