When you imagine ocean sounds, maybe you hear the smooth arcing songs of the humpback whale, or the energetic, rhythmic clicks and snaps of dolphins. But it turns out the oceans are home to a much wider range and diversity of sounds than we could ever imagine, and today some of them are being captured by hydrophones (underwater microphones). In this episode, we take an audio journey of the oceans, learning what sound can reveal, what scientists have yet to identify, and how the underwater soundscape is changing in the Anthropocene.