Building a deep-diving submarine: Pressure hull

Four teams are diving to the deepest part of the ocean, the Mariana Trench, which lies 11km down in the west Pacific.

One of them is a DOER Marine, a marine technology company based in San Francisco.

They are currently putting the finishing touches to the design of their Deep Search submarine.

Here, Liz Taylor, who runs the company, explains why they are using a life-size model of their pressure hull to work out how many people and how much equipment can be packed into their sub.