Abstract: An improved sponson and rigid inflatable boats incorporating the same. The sponson includes a non-inflatable buoyant component, such as closed-cell polyethylene, and an inflatable buoyant component, such as one or more inflatable tubes. The boat includes a rigid hull having sidewalls along which one or more of the improved sponsons extend. In some embodiments, the inflatable component is removably secured to the non-inflatable component by a restraining structure. In some embodiments, the restraining structure includes straps. In some embodiments, the restraining structure includes resilient arms that bias the inflatable component within a pocket formed in the non-inflatable component.