The ornamental design for a middlerail for a watercraft, as shown and described.
FIG. 1 is a perspective view of a middle rail for a watercraft;
FIG. 2 is a cross-sectional/end view of FIG. 1;
FIG. 3 is a front view of FIG. 1;
FIG. 4 is a rear view of FIG. 1;
FIG. 5 is a top view of FIG. 1;
FIG. 6 is a cross-sectional/end view of FIG. 1 as viewed from opposite the view of FIG. 2; and,
FIG. 7 is a bottom view 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.