What is life? What is water? What is sound? In Sounding the Limits of Life, anthropologist Stefan Helmreich investigates how contemporary scientists—biologists, oceanographers, and audio engineers—are redefining these crucial concepts. Life, water, and sound are phenomena at once empirical and abstract, material and formal, scientific and social. In the age of synthetic biology, rising sea levels, and new technologies of listening, these phenomena stretch toward their conceptual snapping points, breaching the boundaries between the natural, cultural, and virtual. Through examinations of the computational life sciences, marine biology, astrobiology, acoustics, and more, Helmreich follows scientists to the limits of these categories. Along the way, he offers critical accounts of such other-than-human entities as digital life forms, microbes, coral reefs, whales, seawater, extraterrestrials, tsunamis, seashells, and bionic cochlea. He develops a new notion of "sounding"—as investigating, fathoming, listening—to describe the form of inquiry appropriate for tracking meanings and practices of the biological, aquatic, and sonic in a time of global change and climate crisis. Sounding the Limits of Life shows that life, water, and sound no longer mean what they once did, and that what count as their essential natures are under dynamic revision.