The ocean known for its islands and atolls formed by coral reefs is the Pacific Ocean. Specifically, it houses numerous tropical islands and archipelagos, such as the Gilbert Islands and the Marshall Islands. These reefs are vital for marine biodiversity, providing habitats for various fish and other marine species. They also play a crucial role in coastal protection by reducing wave impact. The Pacific's coral reefs are under threat from climate change, pollution, and overfishing, leading to ongoing conservation efforts to protect these invaluable ecosystems.