S1, E2: The Great Barrier Reef as a whole coverse an area larger than Great Britain but amazingly only 7% of it is coral reef. The rest is a variety of interconnected habitats including the world's oldest jungle, hundreds of islands, mangrove swamps, mysterious deep water gardens, vast sand flats and meadows of sea grass - all full of amazing wildlife. A giant deep-water lagoon connects all of these, and many of the creatures that live in it are almost impossibly weird - from giant hammerhead sharks to the bizarre 'pearl fish' that lives its live up a sea cucumber's bottom. Marine life here also exists in spectacular profusion, as on the 100 year old shipwreck of the SS Yongala, the greatest wildlife wreck on earth. The connections between all these environments mean that, not only do they depend on each other but, without them the coral reef itself would not survive.