First of all: it's very misleading to describe the Great Barrier Reef as "a living thing".
It's often described as such, but mainly by sensation-seeking websites that should not (IMHO) be used for setting quiz questions. This one, for example.
The Great Barrier Reef is not a single organism; in the words of Wikipedia, it's "composed of over 2,900 individual reefs and 900 islands". Wikipedia also describes the reef as "the world's biggest single structure made by living organisms". Note: not a single organism.
Elsewhere, Wikipedia defines a coral reef as "an underwater ecosystem characterized by reef–building corals."
In other words, the Great Barrier Reef is made up of (probably) millions of living things. As is (for example) the Amazonian rainforest, which I'm pretty sure would be visible from space.
And second of all: the Great Barrier Reef is not in any country. It's in the Coral Sea, which is part of the Pacific Ocean.
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