WIGs (Wing in Ground) are advanced hybrid air cushion crafts and they offer the combination of speed, fuel efficiency, and ride smoothness. WIG rides above the surface like an airplane on a dynamic air cushion that is produced by the vessel's forward motion. The adoption of WIG has been slow due to the complicated technology issues surrounding the vessel; it is a hybrid vehicle that combines marine and aviation theory, wing theory and air cushion theory, aerodynamic and hydrodynamic theory. "WIG Craft and Ekranoplan: Ground Effect Craft Technology" provides comprehensive overview of the design, development and building of WIG vessels."