Philip Ball dives into the magical world of Cornelis Drebbel , inventor of the world's first submarine in 1621. How did the crew of this remarkable vessel manage to breathe underwater, completely cut off from the surface, 150 years before oxygen was officially discovered? King James I of England and thousands of his subjects lined the banks of the River Thames in London to watch the first demonstration. The strangest boat they had ever seen sank beneath the waves and stayed there for three hours. Did Drebbel know how to make oxygen? Historian Andrew Szydlow reveals that Drebbel did have secret knowledge of how to keep the air fresh. In his day, Drebbel was a pioneer of exploring uninhabitable places. Today's equivalent is to make oxygen on the Moon and as scientists grapple with this ultimate challenge, Monica Grady explains their work is being used under the waves where Drebbel began. Producer: Erika Wright.