Shower Basin

FIG. 1 is a front, left and top perspective view of a shower basin, showing my new design; FIG. 2 is a rear, right and bottom perspective view thereof; FIG. 3 is a front view thereof; FIG. 4 is a rear view thereof; FIG. 5 is a left side view thereof; FIG. 6 is a right side view thereof; FIG. 7 is a top plan view thereof; FIG. 8 is a bottom plan view thereof; and FIG. 9 is a front, left and top perspective view of the shower basin in another use state; and, FIG. 10 is an enlarged view of portion 10 of FIG. 1 thereof. The dot-dash broken lines depict the boundaries of the enlargements that form no part of the claimed design.