FIG. 1 is a perspective view of a spa shell showing our design;
FIG. 2 is a second perspective view thereof;
FIG. 3 is a top plan view thereof;
FIG. 4 is a cross-sectional view thereof, taken along line 4-4 of FIG. 3;
FIG. 5 is a cross-sectional view thereof, taken along line 5-5 of FIG. 3;
FIG. 6 is a cross-sectional view thereof, taken along line 6-6 of FIG. 3;
FIG. 7 is a cross-sectional view thereof, taken along line 7-7 of FIG. 3; and,
FIG. 8 is a cross-sectional view thereof, taken along line 8-8 of FIG. 3.
The broken lines in the drawings represent unclaimed portions of the spa shell and form no part of the claimed design.