The ornamental design for a swimmingbooster, as shown and described.
FIG. 1 is a perspective view of a swimming booster showing my new design;
FIG. 2 is another perspective view thereof;
FIG. 3 is a front elevational view thereof;
FIG. 4 is a rear elevational view thereof;
FIG. 5 is a left side devotional view thereof;
FIG. 6 is a right side elevational view thereof;
FIG. 7 is a top plan view thereof;
FIG. 8 is a bottom plan view thereof; and,
FIG. 9 is an enlarged partial view from the right side of FIG. 1.
The broken lines in the drawings depict portions of the swimming booster that form no part of the claimed design. The dash-dot broken lines represent boundaries of the enlarged partial view of FIG. 9 and form no part of the claimed design.