The saying goes that we known more about the surface of the moon than we do about the deep sea - and that's probably true. But modern technologies are opening up the mysterious depths allowing scientists to venture further than ever before into this alien realm. In this special podcast, Helen Scales explores the wonders of the deep with biologist Tim Shank from the Woods Hole Oceanographic Institution in the US. He recently led a pioneering expedition into the deep sea around Indonesia where his team discovered dozens of new species and shed light on extraordinary ecosystems in the dark depths that rival the vibrant coral reefs in sunlit shallows.