An expert and an exponent of free diving gives full background and instructions for penetrating the underwater front, and returning to tell about it. He explains the principles of free diving (neutral buoyancy is essential to free exploration) and discusses the development of equipment in use. He diagrams diseases and describes the dangers of the deep in terms of chemical responses at various levels, control of equipment, weather and water temperature. The unfortunate adventures of colleagues serve as object lessons on safety factors. Diving clubs in the United States, manufacturers and distributors, areas for diving, reasons for diving from sightseer or hunter to explorer, all come in for matter of fact, down to water handling. The French text has been adapted and expanded by an American for American enthusiasts. Authoritative.