A diver inspects coral
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Bleaching threatens world's coral

29 September 2016 Last updated at 06:43 BST

In the Maldives in the Indian Ocean, more than 60% of coral reefs have been left damaged by pollution and rising temperatures.

It's called "coral bleaching" - it happens when the water temperature gets a couple of degrees hotter than normal for two weeks or more - the coral changes colour to white and it's left damaged.

Check out the video and find out more.