Don Walsh and Jacques Piccard (Noaa)
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'At 30,000ft we heard a crack'

Don Walsh recounts his experience of diving to the deepest part of the ocean, the Challenger Deep, 11km down.

On 23 January 1960, two explorers, US navy lieutenant Don Walsh and Swiss engineer Jacques Piccard, became the first people to dive 11km (seven miles) to the bottom of the Mariana Trench.

As a new wave of adventurers gear up to repeat the epic journey, Don Walsh tells the BBC about their remarkable deep-sea feat.