Abstract: The invention provides an improved SWATH type vessel having pontoons and a stern plane located in a position to influence water flow in the region of the tail cone portions of the pontoons and the propellers to reduce depression of the water adjacent the propellers which would otherwise cause propeller ventilation when the vessel is moving at speed.

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.

Abstract: The forward deck of a swath or catamaran type vessel is constructed largely of a sieve-type material, such as honeycomb-type deck grating. Should the foredeck of the vessel, which is normally suspended above the water line become submerged by plowing into a wave, or otherwise inundated by large masses of green water which would otherwise tend to weight the bow of the vessel down, the above deck water will simply drain through the sieve-type material and permit the inherent flotation of the pontoons and hull of the vessel to promptly raise the bow to relative horizontal position.