Mike Corey heads to Australia’s Great Barrier Reef to meet some of the people trying to save it for future generations, including plans for a Great Reef Census - which would see tourist photos used to create the most detailed survey of the structure to date. We meet the scientist whose work on coral spawn could lead to kilometres of dead reef being repopulated, thanks to breakthroughs in robotics; and we find out how submarine rides could be the newest way to see the reef, without causing further harm to it.