1. A lifting body comprising an enclosed hull having a deltashaped planform substantially symmetrical about a plane perpendicular to the direction of the maximum lateral dimension of the lifting body and extending from a nose at one corner of said planform to the mid-point at the wide end opposite the nose, the cross-sections transverse to said plane, on either side being substantially elliptical throughout substantially all of the length of the lifting body, a maximum dimension in said plane and perpendicular to the chord in said plane at a point spaced from said wide end and spaced from the nose, the transverse crosssections of the lifting body progressively increasing in width and decreasing in height from the cross-section at the point of maximum height toward the wide end, and having a large sweep angle Lambda such that under typical operating conditions, and including means providing a surface disposed at a negative dihedral angle Gamma whereby the roll instability resulting from the large sweep angle Lambda is reduced.