This is a textbook aimed at graduate students and offshore engineering practitioners that covers basic fluid mechanics and the deterministic and statistical descriptions of infinitesimal and finite amplitude water waves. It reviews the theory of wave loading on structures and closes with a chapter on the potential of ocean wave energy and devices for extracting it. Since the 1980s there has been tremendous progress in numerical and physical modelling of coastal and offshore structures in waves. This calls for a clear understanding of the phenomena of wave generation, propagation, deformation and its effects on marine structures. This book will help the reader to understand the many results and descriptions found in journals, reports and research papers. It is self-contained, and encompasses the fundamentals of the subject with sufficient description and illustrations.