This work investigates the biological characteristics, behavioral patterns, and ecological roles of cetaceans within their marine environments. The author, Peter H. Rhys Evans, draws upon established zoological research to provide a comprehensive overview of how whales and dolphins have adapted to life in the ocean. The text examines the evolutionary history, physiological traits, and social structures that define these diverse marine mammals.

The subject matter points to a foundational, accessible introduction suitable for readers interested in marine biology and natural history. The framing suggests a focus on clear, descriptive science that balances technical detail with general interest in the lives of cetaceans.