Dr Richard “Harry” Harris has devised a way to push further than anyone else into one of the deepest, darkest, most isolated cold - water cave systems in the world. His secret weapon is using hydrogen as a breathing gas, but hydrogen is so volatile that his support team may, literally, have to pick up the pieces. Either that or they blow out of the water what’s currently possible in diving. In 2018, Harris felt obliged to administer the anaesthetic that was key to the success of the Thai cave rescue. Against his expectations, all the boys and their soccer coach were delivered safely to their families. Harris may not make it back to his own family and it begs the question of why he’s choosing to be a human guinea pig.