Can mapping the Great Barrier Reef help it survive?

After three recent mass bleaching events, the future of Australia's Great Barrier Reef is in the balance - with a senior scientist saying that it's "calling for urgent help".

But now scientists and activists have united to try to help it regenerate itself.

Only 5-10% of the reef is regularly surveyed, and so volunteers - including divers and tourists - have been asked to take thousands of photos, which will be put online and categorised, again by volunteers.

This should allow conservationists to link up areas that are still healthy with areas which are struggling, during its annual spawning event in December, which sees it release trillions of eggs and sperm into the ocean like an underwater snowstorm.