A lagoon is a shallow body of water separated from a larger body of water, such as an ocean or sea, by a barrier like a sandbar, coral reef, or barrier island. These calm waters are often rich in biodiversity and provide a habitat for various marine life, including fish, birds, and plants. Lagoon ecosystems can be found in tropical and temperate regions around the world. They play a crucial role in coastal protection, water filtration, and serving as nurseries for young fish. Notable examples of lagoons include the Venetian Lagoon in Italy and the Great Barrier Reef lagoons in Australia.