* Amphibians: Amphibians are animals that can live both in water and on land. They have lungs, but they also have gills when they are young. Amphibians include frogs, toads, salamanders, and newts.
* Reptiles: Some reptiles, such as turtles and crocodiles, live in water. They have lungs, but they can also hold their breath for long periods of time.
* Mammals: A few mammals, such as dolphins, whales, and seals, live in water. They have lungs, but they can also hold their breath for long periods of time.
* Invertebrates: Invertebrates are animals that do not have a backbone. Many invertebrates live in water, including jellyfish, worms, and crabs.