The ornamental design for a waterblaster, as shown and described.
FIG. 1 is a reduced scale perspective view of a water blaster showing of my novel and non-obvious design.
FIG. 2 is a front elevational view thereof.
FIG. 3 is a rear elevational view thereof.
FIG. 4 is an elevational view of one side thereof.
FIG. 5 is an elevational view of another side thereof.
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The broken lines shown around the borders of and internally within the FIGURES are merely illustrative purpose only and form no part of the claimed design.