A towfish, or deep-water detector, being launched
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EgyptAir crash: How do you recover wreckage from the sea?

Families waiting to find out why they lost relatives in Flight MS804 are unlikely to get any definitive answers until the plane's black box is found.

The BBC's Richard Westcott has been out with a team of oceanographers to find out how difficult is it to identify and recover wreckage from the sea.

Go to next video: EgyptAir - what do we know?