In the middle of the Indian Ocean lies some of the last coral reef wilderness on Earth. The Chagos Archipelago, a collection of atolls, including Earth's largest—the Great Chagos Bank—is home to reefs that have been largely undisturbed by humans for the last 50 years. Some estimates indicate the Chagos Archipelago may contain more than half of the healthy coral reefs remaining in the entire Indian Ocean. These reefs are protected both by their remote location, and in one of the world's largest no-take marine reserves—the British Indian Ocean Territory (BIOT) marine protected area.
source https://phys.org/news/2021-03-remote-coral-reefs-earth.html