Finding the wreck of the Titanic would be a career-defining achievement for most people. For oceanographer Robert Ballard, it's just one chapter in a life packed full of extraordinary marine exploration. Bob located the world-famous shipwreck in 1985, but even before that, he’d helped prove the existence of hydrothermal vents: underwater formations surrounded by ecosystems flourishing in the ocean’s depths - without sunlight; a discovery that revolutionised our understanding of where and how life can flourish... Over a career spanning six decades, Bob has pioneered revolutionary technologies, discovered some of history's most famous shipwrecks and inspired new generations of explorers. What's more, as he tells Professor Jim Al-Khalili, he's still exploring mysteries of the deep today...