CBS News took a dive and found a scene as busy as Broadway. You see more life forms jammed into a square foot of the reef than just about any place on Earth. The reef is made up of more than 400 different kinds of coral and hosts some 5,000 species of fish.
It's full of predators, and fish just going along for the ride. It's that balancing act of nature that holds the reef together.
But that act might be in real danger of collapsing. One of the most serious, immediate threats to the reef looks like it fell from the sky. It is the Crown of Thorns starfish, which eats coral right down to the bone.
"The Crown of Thorns starfish, here is a natural predator of coral reef systems," says Udo Engelhardt, the leading expert on the starfish's impact on the reef. "Basically, you find them from the Indian Ocean right across to the Pacific Ocean."
"This little beasty is incredibly well adapted for what it's doing, very efficient predator, for sure," he says. "I mean, if someone would have to design a coral predator today, this is the design you would want."
A mature female starfish in one breeding season may produce 60 to 70 million eggs, a phenomenal output.
Engelhardt took Simon down to a stretch of reef that was doing just fine until a few months ago when a battalion of starfish came in for the kill. Scientists are searching frantically for clues as to why the Crown of Thorns variety is suddenly such a threat. It used to feed on the reef in regular 15-year cycles, giving the coral time to recover between attacks. Now, those starfish come back sooner and in greater numbers.
To see how difficult it is to fix a reef once it starts to go wrong, you only have to look at the efforts to kill off the Crown of Thorns starfish. Divers hunt starfish and inject them with a biodegradable poison that doesn't hurt the coral. But tackling a large area would be like trying to weed Nebraska's cornfields by hand.
The starfish are eating the reef, but scientists believe that people may be the starfish's best ally, by changing the water chemistry in a way that's a lot better for starfish than for coral. The pattern is well documented around the world, whether it's overfishing in the Philippines or pollution in the Caribbean. People are killing off the world's reefs.
Australia's coastline is full of cattle ranches and sugar cane farms that pump waste products into the water and change the balance of nature miles away on the reef.
It's not just farmers who threaten the reef. Fishermen are just as big a problem. The whole reef area is very rich in very large prawnsand prawns are a very lucrative cash crop.
But after just 13 passes on one area, one boat can remove up to 95 percent of the living organisms beneath it. It's against the law for trawlers to cast their nets near the reef, but that doesn't stop them.
And then there are the tourists, coming in record numbers, more every year. The trick is to prevent them from destroying the beauty that brought them here in the first place. They pump millions of dollars into the Australian economy and leave (Australians hope) with an interest in seeing the reef protected.
But it's not that simple. Every plan to bring in more tourists starts a new fight over who should get which piece of the reef.
"I want proper environmental controls," says Keith Williams, sounding like an environmentalist crusader. But to Australia's green movement, he's just the opposite. He's a member of that dreaded species, the developer. He lives on the Gold Coast, a resort he knows well - because he built it.
It was Williams' plan to build yet another resort near the reef that brought him head to head with conservation groups.
He says, "These people have blood in their eyes about me personally, and they'll do anything, anything to stop what I'm doing."
Williams had the bulldozers, but his opponents had a secret weapon, a 71-year-old woman named Margaret Thorsborne. She was convinced Williams was bulldozing some of the area's most beautiful coastline. And it seemed that every time the construction workers wanted to remove a tree, they had to remove her first.
"I think it's time older people didn't leave it for the young," she says. "We aren't the last generation on Earth, but sometimes we act as if we are,...with no thought for the future."
In Jamaica, the future has already happened. Jamaica's coral reef was reasonably healthy in the '70s, but today that reef is not geology. It's history. And it took just 20 years.
"We can do bad things in a short amount of time," observes Bill Dennison, an expert on coral. He grew up in Ohio, a place not known for its marine life. But he has spent his career studying the destruction of coral reefs from Thailand to Florida.
The Great Barrier Reef has gotten a bad rap, in a sense, as a reef for the rich. Australia is far. Getting there is expensive. And once you arrive, you can't see it. You have to go diving, which costs even more money.
So why should Americans - or anyone else, for that matter - care when there is so much else to worry about?
The answer is simple: It's the only one there is.
"I think the Great Barrier Reef will be one of the last places on Earth to have an intact functioning coral reef," predicts Dennison. "It's such an amazing sight,...a coral reef and particularly to be immersed in a coral reef."
"We're attracted to living things, and a coral reef is the ultimate in that because everything you see,...everything you touch, is because f living things. You're immersed in the water,...surrounded by living things,...looking at life in its fullest," Dennison adds.
The experts are warning that people must change their approach to life on the Australian coast. If not, some day the Great Barrier Reef could become the Not So Great Barrier Reef, or perhaps no reef at all.