Jim McMahon/Mapman®

Deep-sea explorers made a surprising discovery while mapping the Pacific Ocean. Off the coast of an island called Tahiti, divers found a new, healthy coral reef. 

Experts believe it has been around for at least 25 years, but divers didn’t discover it until this past November. The coral reef is deep in the ocean, between 100 and 230 feet below the surface. 

Its location kept the reef hidden, and scientists say it also helped keep the reef safe. The deeper you go in the ocean, the cooler the water. Reefs in more shallow waters are in danger because of rising ocean temperatures.

Corals look like plants, but they are actually tiny animals. Their hard outer skeletons form reefs. They get their nutrients—and colors—from tiny plantlike organisms called algae. When the ocean gets too warm, corals release the algae and turn white. This process, called coral bleaching, can kill reefs.

Coral reefs are important ecosystems. Though they cover less than 1 percent of Earth’s ocean floors, they’re home to about one-quarter of all marine species. Scientists say finding a healthy new reef is good news.