Aquatic animals are creatures that live in water, including oceans, rivers, lakes, and ponds. They can be divided into two main groups: fish and invertebrates. Fish have gills that allow them to breathe underwater, while invertebrates, such as jellyfish and crabs, do not have a backbone. These animals play essential roles in their ecosystems, helping to maintain the balance of aquatic life. Many aquatic animals are adapted to their environments. For example, whales and dolphins are mammals that breathe air but live in the ocean. Some species, like frogs, can live both in water and on land, showcasing the diversity of life in aquatic habitats.