Underwater worlds refer to the diverse ecosystems found beneath the surface of oceans, seas, and lakes. These environments are home to a wide variety of life forms, including fish, corals, and marine mammals. The most well-known underwater world is the Great Barrier Reef, which is the largest coral reef system on Earth and supports thousands of species. These ecosystems are vital for maintaining the planet's health, as they produce oxygen and help regulate climate. Additionally, underwater worlds provide resources such as food and medicine. Conservation efforts are essential to protect these habitats from threats like pollution and climate change, ensuring their survival for future generations.