This work investigates the biological adaptations, social behaviors, and ecological roles of marine mammals within the global ocean environment. Jacques-Yves Cousteau, a pioneer in underwater exploration and marine conservation, utilizes his extensive field research and direct observations to document the lives of whales, dolphins, seals, and other aquatic mammals. The book presents a framework for understanding these creatures not merely as biological specimens, but as complex, intelligent inhabitants of a fragile and interconnected marine ecosystem.

This text is regarded as a foundational entry in popular marine science, reflecting Cousteau's signature blend of technical observation and environmental advocacy. The material provides a highly accessible entry point for readers interested in the complexities of marine life as documented by one of the twentieth century's most prominent oceanographers.