Named for its staggering biomass and diversity of corals, this region encompasses the Great Barrier Reef — the world’s “largest living thing” — and was declared a UNESCO World Heritage Site in 1981. Located off the northeastern coast of Australia, the Coral Sea hosts an exquisite variety of vibrant coral reefs, remote islands, towering underwater mountains and deep-sea canyons. Among the corals, it is home to whales, dolphins, sea turtles, rays, sharks and seabirds, and it's one of the last known places on Earth where big fish can still be found in healthy numbers. Threats include land-based runoff, overfishing and coastal development, but the Australian government took action in July 2018 to establish part of it as the Coral Sea Marine Park, now known as one of the world's largest protected areas!