Building a deep-diving submarine: Design
Four teams are diving to the deepest part of the ocean, the Mariana Trench, which lies 11km (7 miles) down in the western Pacific.
One of them is DOER Marine, a marine technology company based in San Francisco.
They are currently putting the finishing touches to the research phase of their Deep Search submersible.
Here, Liz Taylor, who runs the company, describes the factors that have driven the design of the sub.
- BBC News