This book furthers academic scholarship in cutting-edge areas of geographical and geopolitical writing by drawing on a series of little-studied undersea living projects conducted by the US Navy during the Cold War (Project Genesis, Sealab I, II and III). Supported by an engaging and novel empirical setting, the central themes of the book revolve around the practice and construct of ‘territory’, ‘terrain’, the ‘elemental’ and the interrelationships between these material phenomenon and both human and non-human bodies. Furthermore, the book will point to future research trajectories in the form of ‘extreme geographies’ to better understand living practices in a world that is increasingly submerged and extreme.Table of Contents: 1. Introduction: Towards the ‘Deep Dark Sea’ 2. ‘Taking Chances for all of Mankind’: Taming the Underwater Frontier 3. Domesticating and Dishwashing: Making Home on the Seafloor 4. ‘A Breed Apart’: Taking the Measure of Man 5. ‘Think Helium’: Submarine Pressures and Elemental Entanglements 6. Companions, Zappers, and Invaders: The Animals of Sealab 7. From Sealab to Skylab: Inhabiting Extremes 8. Conclusions