Book excerpt: Air Lubrication and Air Cavity Technology is a major development that has emerged in recent years as a means to reduce resistance and powering for many types of ships, and an efficient design for high speed marine vessels. This book introduces the mechanisms for boundary layer drag reduction and concepts studied in early research work. Air bubble and sheet lubrication for displacement vessels is outlined and the key projects introduced. Generation of low volume flow air cavities under the hull of displacement, semi displacement and planing vessels are introduced together with theoretical and empirical analysis and design methods. Resistance reduction, power reduction and fuel efficiency are covered for both displacement and high speed vessels. Air layer and air cavity effects on vessel static and dynamic stability are covered, linked to regulatory requirements such as IMO. Seaway motions and reduced impact load of high speed craft in waves are discussed including model test results. Integration of propulsion systems for optimum powering is summarized. A design proposal for a wave piercing air cavity craft is included in an appendix. A comprehensive listing of document resources and internet locations is provided for further research.