How can we save the occupants of stricken submarines? What species survive in the deepest depths of ocean trenches? Recognising the centenary of the Titanic tragedy, we're diving deep to meet the Rolls-Royce NATO Submarine Rescue System, we find out about a new initiative to discover what really lives at the bottom of the ocean and hear how volcanoes are acidifying the seas. Plus, what robots can tell us about cocktail party conversations, the mystery of the pigeon's magnetic navigation, and can oil-based face-cream make you fat...?