This work investigates the complex biological mechanisms and behavioral strategies utilized by marine organisms to survive in the competitive environment of the world's oceans. Jacques-Yves Cousteau, a pioneer in underwater exploration and marine research, draws upon decades of direct observation and scientific documentation to explain how predation and defense shape marine ecosystems. The book presents a framework for understanding the evolutionary pressures that drive the development of camouflage, armor, and specialized hunting techniques in aquatic species.

This text is regarded as a foundational entry in the popular science literature of the mid-20th century, reflecting Cousteau's expertise in underwater observation. The framing suggests an accessible yet rigorous introduction to marine biology that remains relevant for readers interested in the mechanics of natural selection within aquatic environments.