The ornamental design for an upperrail for a watercraft, as shown and described.
FIG. 1 is a perspective view of an upper rail for a watercraft;
FIG. 2 is a cross-sectional/end view of the upper rail for a watercraft of FIG. 1;
FIG. 3 is a front view of the upper rail for a watercraft of FIG. 1;
FIG. 4 is a back view of the upper rail for a watercraft of FIG. 1;
FIG. 5 is a top view of the upper rail for a watercraft of FIG. 1;
FIG. 6 is a cross-sectional/end view of the upper rail for a watercraft of FIG. 1 as viewed from opposite the view of FIG. 2; and,
FIG. 7 is a bottom view of the upper rail for a watercraft of FIG. 1.
The broken away symbols in the drawings indicate the appearance of any portion of the article between the break lines forms no part of the claimed design.