In the Front Viewport, move it (Pool Bottom) to down with Move tool.
Now, select the Pool Wall object. In the modifier stack, go to its Spline sub-object mode. Then, in the viewport click on the spline to select the Spline sub-object. It will turn red. In the modify panel scroll down and type the value of the Outline = -10 and press Enter.
Now leave the Spline sub-object mode. Maximize the Perspective viewport for better viewing. Add an Extrude modifier to it. Set the Amount = -58.
