Blue hole
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Aerial video of 'world's deepest' underwater sinkhole in South China Sea

27 July 2016 Last updated at 10:49 BST

This stunning aerial video shows the world's deepest underwater sinkhole, according to scientists in China.

Researchers studying the "blue hole" in the South China Sea reckon that it is 300 metres deep.

The team says it looked at things like tidal water levels and temperature to work out the depth.

Until now, the deepest known blue hole was Dean's Blue Hole, which is 202 metres deep and in the Bahamas in the Caribbean.