The most famous tourist places number two is great Barrier Reef pictures in Australia

 A NATURAL WONDER of the world, stretching more than 1,600 miles, the Great Barrier Reef is the world’s largest organically formed structure. Last month, after years of dreaming about it, I had the opportunity to dive the reef and come face to face with some of the most beautiful underwater landscapes I’ve ever seen.

The experience has a way of spontaneously filling memory cards. In that spirit, here are 44 images I took during my time on the Great Barrier Reef, off the coast of Queensland, Australia.

 Nemo
Finding Nemo is one of the first things you want to do when you dive the Great Barrier Reef. Around the world, these poor fish have probably been extremely confused as to why, for the past 10 years, everyone has been getting in their face for a photo.

Not far beneath the surface of the Coral Sea, where the Great Barrier Reef lives, parrotfish teeth grind against rock, crab claws snap as they battle over hiding spots, and a 600-pound grouper pulses its swim bladder to announce its presence with a muscular whump. Sharks and silver jacks flash by. Anemone arms flutter and tiny fish and shrimp seem to dance a jig as they guard their nooks. Anything that can't glom on to something rigid is tugged and tossed by each ocean swell.

The reef's sheer diversity is part of what makes it great. It hosts 5,000 types of mollusks, 1,800 species of fish, 125 kinds of sharks, and innumerable miniature organisms. But the most riveting sight of all—and the main reason for World Heritage status—is the vast expanse of coral, from staghorn stalks and wave-smoothed plates to mitt-shaped boulders draped with nubby brown corals as leathery as saddles. Soft corals top hard ones, algae and sponges paint the rocks, and every crevice is a creature's home. The biology, like the reef, transforms from the north—where the reef began—to the south. The shifting menagerie is unmatched in the world.

Time and tides and a planet in eternal flux brought the Great Barrier Reef into being millions of years ago, wore it down, and grew it back—over and over again. Now all the factors that let the reef grow are changing at a rate the Earth has never before experienced. This time the reef may degrade below a crucial threshold from which it cannot bounce back.

 The bad news is that the Great Barrier Reef is being threatened by over-fishing, manmade pollution, and warming ocean temperatures linked to climate change. Scientists estimate that the Great Barrier Reef will reach a point of unalterable damage by 2030 if action isn’t quickly taken to mitigate the sources of these issues.

The good new is, World Wildlife Fund is helping to do just that with several Australia-based conservation groups. This green turtle that can take you on a virtual ride though the magnificent underwater world is part of their research program that aims to understand how pollution and environmental factors are impacting the reef and the turtle population. Seeing the ocean floor from a turtle’s perspective in this video is a great reminder of what we stand to lose if we don’t step in to protect this amazing ecosystem.