a control fin assembly for a water vehicle includes a multiplicity of finsonnected together and grouped in an array mounted on the vehicle . a portion of the array is of a shape - memory material responsive to heat to assume selected shapes different from the shape of the array portion otherwise . the array portion is electrically conductive and adapted to increase in temperature upon application of electrical current thereto to effect the assumption of the selected shapes . the invention further relates to a control fin for a water vehicle , at least a portion of the fin being of a shape - memory material responsive to heat to assume selected shapes different from the shape of the fin otherwise , the fin portion being electrically conductive and adapted to increase in temperature upon application of electrical current thereto to effect the assumption of the selected shapes .