Sylvia Earle, one of the world's great oceanographers, makes a rare appearance in this special event. She has walked untethered on the sea floor at a depth lower than any other human, and was Time magazine's first 'hero of the planet' in 1998. Earlier in her career, Sylvia led the first ever team of women aquanauts. As well as an explorer extraordinaire, she is also a campaigning voice for research into marine life, and the author of over 100 books including Exploring the Deep Frontier, Sea Change and The Atlas of the Ocean (2001). She is currently Explorer in Residence at the National Geographic Society at the age of 75.