Deep underground in the wilderness of New Zealand, gigantic and largely unexplored cave systems attract adventurers and cavers from around the globe. Kieran McKay and his team set out on an almost impossible journey to try to find a connection between two cave systems. If they happen to track down the link between the Nettlebed and Stormy Pot systems, roughly 80 missing metres, they could claim credit for having found the deepest cave in the southern hemisphere. But 80m can become a mind-boggling odyssey, hampered by tight squeezes, the unexpected inrush of water and a total lack of communication with the world outside…