Underwater ecosystems are diverse environments found beneath the surface of oceans, rivers, and lakes. They include habitats like coral reefs, kelp forests, and freshwater wetlands, each supporting a variety of plant and animal life. These ecosystems play a crucial role in maintaining biodiversity and providing resources such as food and oxygen. Coral reefs, for example, are often called the "rainforests of the sea" due to their rich biodiversity. They are home to many species, including fish, mollusks, and sea turtles. Other important underwater ecosystems, like seagrass beds and mangroves, also contribute to coastal protection and serve as nurseries for marine life.