The ornamental design for a watercraft, as shown and described.
FIG. 1 is a front right perspective view with one chair in a raised position and one chair in a lowered position of a watercraft showing our new design;
FIG. 2 is a front right perspective view of thereof with 3 doors in an opened position;
FIG. 3 is a front right perspective view thereof with 3 doors in an opened position;
FIG. 4 is a back right perspective view thereof with 2 doors in an opened position and all chairs in a lowered position;
FIG. 5 is a top plan view of FIG. 3;
FIG. 6 is a bottom plan view thereof;
FIG. 7 is a right side view thereof;
FIG. 8 is a left side view thereof;
FIG. 9 is a front side view thereof; and,
FIG. 10 is a back side view thereof.
Portions of the article shown in broken lines form no part of the claimed design.