More people have died to explore underwater caves than climbing Mount Everest, and they know more about deep space than they do about the depths of the oceans. From one of the top cave divers working today, and one of the very few women in her field, blends science, adventure, and memoir to bring listeners face-to-face with the terror and beauty of earth's remaining unknowns and the extremes of human capability. Jill Heinerth, the first person in history to dive deep into an Antarctic iceberg and leader of a team that discovered the ancient watery remains of Mayan civilizations, has descended farther into the inner depths of this planet than any other woman. She takes listeners into the harrowing split-second decisions that determine whether a diver makes it back to safety, the prejudices that prevent women from pursuing careers underwater, and her endeavor to recover a fallen friend's body from the confines of a cave.