The ornamental design for a waterfilter, as shown and described.
FIG. 1 is a perspective view of a water filter according the present invention;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a top view thereof;
FIG. 5 is a bottom view thereof;
FIG. 6 is a left view thereof; and,
FIG. 7 is a right view thereof.
In the drawings, the broken lines depict portions of the water filter; that form no part of the claimed design. Portions not shown in the drawings are not visible during use and form no part of the claimed design.