The ornamental design for a watercraftbow, as shown and described.
FIG. 1 is a perspective view, taken from a front, left side of a watercraft bow according to our design;
FIG. 2 is a top plan view thereof;
FIG. 3 is a front elevation view thereof;
FIG. 4 is a left side elevation view thereof, a right side elevation view being a mirror image of the left side elevation view; and,
FIG. 5 is a bottom plan view thereof.
The dashed lines showing portions of the watercraft bow form no part of the claimed design; and the dotted/dashed lines illustrate the bounds of the claimed design and form no part thereof.