The term for creatures that live both in water and on land is "amphibians." This group includes animals such as frogs, toads, salamanders, and newts. Amphibians typically undergo a life cycle that starts in water, where they hatch as eggs and often begin as larvae with gills. As they mature, they adapt to terrestrial life, developing lungs for breathing air. This dual lifestyle allows amphibians to exploit both aquatic and terrestrial ecosystems. They play vital ecological roles, serving as both predator and prey, and are often indicators of environmental health due to their sensitivity to pollutants.