The Great Barrier Reef is home to thousands of marine species.

You can spend a lifetime exploring the Great Barrier Reef and still not see all of this colorful coral realm—it’s nearly the size of Montana. Sprawling off the east coast of Queensland, Australia, the Great Barrier Reef is not a single reef but a group of more than 2,800 distinct entities. It stretches over 1,250 miles (2,000 kilometers) north to south and covers some 135,000 square miles (350,000 square kilometers) in total.

The reef system is the largest structure on Earth built by living organisms, tiny hard corals that are no bigger than a fingernail. When corals die in countless numbers their limestone-secreted skeletons build upon one another to form the bedrock of the reef. The magnificent structures we see today were produced by a slow process played out over millions of years. Reefs grow only about half an inch (1.3 centimeters) a year.

Some 2,000 different fish species have been identified on the Great Barrier Reef, and new ones are found each year. Scientists estimate that the reef is home to 4,000 mollusk species and over 250 different shrimp species. Even the corals that construct the reef itself are diverse—numbering some 400 species.

This colorful aquatic ecosystem is home to a staggering diversity of plant and lower animal life but is also frequented by larger species like dugongs, sea turtles, sharks, and dolphins.

In order to protect these biological treasures, the Great Barrier Reef Marine Park was designated a World Heritage site in 1981. Some two million tourists visit the Great Barrier Reef each year, driving an eco-economy that generates billions of dollars annually. But in recent years, the reef has suffered unprecendented coral bleeching. [Related: Tourists Try to See Great Barrier Reef Before It's Gone]

<p><br> Hordes of divers and other tourists descend on the Great Barrier Reef each year, but with modest environmental impact thanks to strict regulations. A much greater threat is climate change—sea-temperature rise, acidification, and more intense events such as cyclones are putting the reef at risk.</p>

Reef Rider


Hordes of divers and other tourists descend on the Great Barrier Reef each year, but with modest environmental impact thanks to strict regulations. A much greater threat is climate change—sea-temperature rise, acidification, and more intense events such as cyclones are putting the reef at risk.

Photograph by Pete Atkinson, Getty Images

How to Get There

Most day trips to the reef leave on boats from coastal centers like Cairns or Port Douglas. Most of the reef is dozens of miles offshore and must be reached by boat journeys of one to several hours.

When to Go

The Great Barrier Reef lies in tropical waters where temperatures are warm enough to offer enjoyable swimming and diving year round—though averages can vary 10°F (5.5°C) from winter to summer. Peak tourism time on the reef is April through November, but even in winter ocean water temperatures typically top 72°F (22°C). Daytime temperatures during the summer months (December to March) can be quite hot—particularly in the northern regions of the reef.

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How to Visit

High-speed catamarans take day-trip visitors to the reef, often docking at special base camp platforms equipped for snorkeling, diving, or exploration via glass-sided semi-submersibles. Other boat tours, including sailboats, provide a more leisurely experience. Private charters are available for snorkeling, diving, whale watching, or fishing adventures—including overnight live-aboard vessels for journeys to more remote locations. Aircraft and helicopter flights offer a bird's-eye view of the massive reef system, much of which lies close to the surface in clear, warm waters.

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