The ornamental design for a petpool, as shown and described.
FIG. 1 is a front view of a pet pool, showing my new design;
FIG. 2 is rear view thereof;
FIG. 3 is a left side view thereof;
FIG. 4 is a right side view thereof;
FIG. 5 is a top plan view thereof;
FIG. 6 is a bottom plan view thereof;
FIG. 7 is a perspective view thereof; and,
FIG. 8 is an enlarged view of portion 8 shown in FIG. 7.
The evenly spaced broken lines in the drawings depict portions of the pet pool that form no part of the claimed design. The unevenly spaced broken lines in the drawings define the boundary of the enlarged portion shown in FIGS. 7 and 8 and form no part of the claimed design.