In the summer of 1942, an extraordinary group of men united to form an exceptional unit. Known as the Maritime Unit, it comprised America's first swimmer-commandos- an elite breed of warrior-spies who were decades ahead of their time when they created the tactics, technology, and philosophy that live on in today's Navy SEALs. Often armed only with knives and wearing nothing more than swim trunks and flippers, the Maritime Unit's combat swimmers and other operatives carried out seaborne clandestine missions in the Atlantic, Pacific, and Mediterranean theatres of World War II. In First SEALs , Patrick K. O'Donnell unearths their incredible history- one of the greatest untold stories of World War II.