The ornamental design for a personal watercraft, as shown and described.
FIG. 1 is a perspective view of the personal watercraft of the instant invention;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The broken lines shown in the figures (portions of the design shown in broken/dashed lines) are included for the purpose of illustrating environment and form no part of the claimed design.