Abstract: An improved hull construction for a SWATH vessel of the type having first and second pontoons disposed beneath a superstructure and coupled thereto by vertically disposed struts. The improvement comprises substantially hollow sponson whose bottom surface defines a relatively narrow horizontally extending strake disposed between the superstructure and each pontoon for producing forces to right the vessel including substantially instantaneously increasing the rate of buoyancy as the superstructure contacts the water surface. In the preferred embodiment, each sponson extends fore and art of the vessel for substantially the entire length of the struts, and includes a bottom surface defining a strake located a prescribed distance below the superstructure for increasing the waterplane area by a prescribed amount when the bottom surfaces of the sponsons contact the water's surface.