Three years ago travel writer Lydia Gard discovered freediving almost by accident. It's an extreme and beautiful sport defined by one simple objective: to dive as deep as you can on one single breath. Record holders are now routinely diving to more than 120 metres, pushing the sport and their bodies to find out what's humanly possible. Through her coach, Lydia was drawn into a small but fanatical community of competition athletes all united in their drive for depth, and that's where she stumbled on a darker side of the sport. Rumours swirled that a group of top divers were doping to get deeper, faster. As the community began to turn on each other over the allegations, one prominent diver decided to take the law into his own hands. A secret sting operation was meant to put an end to the problem by bringing the alleged dopers out of the dark, and into the light. But the issue hasn't gone away. And now, a lot of people who've been too scared to speak up, are ready to talk.