FIG. 1 is a top perspective view of a bath tub shelf showing my new design;

FIG. 2 is an enlarged top plan view thereof;

FIG. 3 is an enlarged rear elevational view thereof, taken in the direction of the arrow of FIG. 2;

FIG. 4 is an enlarged left side elevational view thereof, the right side being a mirror image of that shown;

FIG. 5 is an enlarged front elevational view thereof; and,

FIG. 6 is an enlarged bottom plan view thereof.