In 2007, our guest, Fabrice Schnoller, was sailing off the coast of Mauritius when he had an encounter that would change his life and open a new frontier in marine biology. As his boat neared land, huge pillars of steam burst out of the water. When Schnöller jumped in to investigate, he was overwhelmed by a crashing, creaking sound. It was the echolocation clicks of sperm whales, the bearers of the largest brains ever known to have existed on Earth. In addition to helping whales navigate, some evidence suggests that these clicks also function as a language. To investigate this possibility, Schnöller founded DAREWIN, the first initiative devoted to studying whale click communication and exposing it to the wider public. In the nine years since the project launched, Schnoller and his team have amassed the largest database of sperm whale vocalizations in history — all collected non-invasively, through free-diving. We speak with Schnöller about DAREWIN’s work, its pioneering methodology, and what it’s like to be X-rayed by a whale.