As a child, Jill Heinerth dreamed of being an astronaut. As a Canadian girl growing up in the twentieth century, this option didn’t seem accessible to her. Instead of a career that blasted her far above the Earth’s surface, she forged her own path deep within the Earth. She discovered a place where she could still explore hidden worlds, floating weightlessly. Although water is the lifeblood of our planet, we somehow know more about the cosmos than we do about our Earth’s own underwater caves.