Final answer:
Aquatic animals live in water environments such as the sea, lakes, and rivers, with aquatic biomes divided into freshwater and marine ecosystems based on salt content.
Step-by-step explanation:
The natural habitat of animals classified as aquatic is in the water, which includes both the sea and freshwater environments like lakes, streams, rivers, and ponds. Aquatic animals are adapted to living in these environments with varying salt concentrations. Aquatic biomes are broadly categorized into freshwater and marine ecosystems. Freshwater biomes contain less than 1% salt and include environments such as ponds, lakes, streams, rivers, and wetlands. On the other hand, marine ecosystems are characterized by higher salt concentrations and include the oceans, coral reefs, and estuaries.