The Sea Shadow incorporates a Small Water Plane Area Twin Hull (SWATH) hull form with canted struts extending below the water line to torpedo-shaped hulls. The design allows for exceptional sea keeping performance. Fins mounted on the front and back of the inboard sides of the lower hulls provide the control surfaces for turning the vehicle, eliminating the need for conventional rudders and reducing drag. The ship's sloped sides are an extension of the angled struts, whose design are driven by signature, hydrodynamic and structural considerations. Several technologies from the Sea Shadow have been incorporated into Navy ships including signature control on Arleigh Burke-class destroyers. Also, Sea Shadow's Small Waterplane Area Twin Hull (SWATH) technology has been incorporated into the TAGOS-19, a twin hull ocean surveillance ship.
http://www.globalsecurity.org/military/systems/ship/sea_shadow.htm
