A watercraft safety flag assembly comprising a flexible planar visibility-enhancing element having a forward edge and a rear edge spaced from the forward edge by a width, and a rigid planar stiffening element secured to the flexible planar visibility-enhancing element, where the planar stiffening element substantially spans the width of the flexible planar visibility-enhancing element and is configured to provide maximum stiffening proximate the forward edge, minimal stiffening proximate the rear edge, and decreasing stiffening with increasing distance from the forward edge. There is also provided a header element joined to the forward edge of the flexible planar visibility-enhancing element and which forms a cylindrical sleeve for receiving a mast, where the rigid planar stiffening element extends into the cylindrical sleeve formed by the header element.