This book begins by tracing the evolution of energy systems?from traditional fossil fuels to the rise of land-based renewables?and highlights the spatial and societal pressures that hinder further terrestrial expansion. It then introduces the ocean as a promising frontier for renewable energy generation. The core of the book is structured into four main chapters, each dedicated to a key marine renewable energy type: offshore wind turbines, wave energy converters, tidal energy converters, and floating solar farms. Each chapter explores the fundamental principles, system components, design considerations, and challenges unique to ocean environments. The final chapters examine emerging future directions, including hybrid renewable systems, offshore hydrogen production, clean fuels and maritime decarbonization, and the role of digital technologies in offshore system monitoring, management and maintenance.