This presentation shares a participatory workshop on listening to and re-mapping coral reef soundscapes through co-creative, speculative instrument-making, developed in collaboration with the Horniman Museum and Gardens, London. Drawing on marine bioacoustic research showing that coral larvae and juvenile fish orient toward the complex sounds of healthy reefs to locate places to settle, the workshop invites participants to dwell with the gradual loss of these acoustic environments. The session explores listening as a relational practice in the face of ecological loss, and negotiates acts of collective instrument-making as a form of situated, tacit knowledge production that foregrounds embodied, relational modes of engagement with more-than-human worlds.