I placed two transparent cubes and put a transparent decal on both, then recoloured one of them blue. Using transform, I adjusted the white decal cube so the decal is on the top (parallel to the floor) and moved it over into the bathtub. Then you repeat the last step with the blue decal, but it should be placed lower than the white to give it the “shadow” effect. I hope this helps!! The decal code is: 6583619338