James Cameron on why he plans to dive to the Mariana Trench

Hollywood director James Cameron may be close to making a dive to the deepest place on Earth.

In a one-man submarine, he plans to journey 11km (seven miles) down beneath the waves to the bottom of the Mariana Trench, in the western Pacific.

Mr Cameron and his team have just set sail to reach the trench and are now waiting for a clear stretch of weather to begin the dive.

But before set off, he spoke to the BBC's Rebecca Morelle about why he wants to make the risky dive.

Click to see more of the BBC's special report on the race to the bottom of the ocean.