The oceans were restless in the years leading up to World War II. Beneath their surface, the United States Navy was building a silent service that would eventually become the prowling teeth of Pacific warfare. But in those early days, undersea warfare was still uncertain, its technology complex and often unforgiving. No story better captures the peril, perseverance, and power of this era than the journey of a submarine that bore two names: first as a tragedy, and then as a warrior. This is the story of USS Sailfish, known to ghost and legend as Squalus.