Answer: France
Notes: The New Caledonia Barrier Reef is located in New Caledonia, an overseas collectivity of France located in the southern Pacific Ocean. It is the longest continuous barrier reef in the world and the third-largest after the Great Barrier Reef of Australia and the Mesoamerican Barrier Reef. These Lagoons are of exceptional natural beauty. They feature an exceptional diversity of coral and fish species and a continuum of habitats from mangroves to seagrasses with the world’s most diverse concentration of reef structures. The Lagoons of New Caledonia display intact ecosystems, with healthy populations of large predators, and a great number and diversity of big fish. They provide habitat to a number of emblematic or threatened marine species such as turtles, whales or dugongs whose population here is the third-largest in the world.
