"Where is the watermark data in the RGB data" It is distributed all over the RGB data of the image, the watermark slightly alter the values of each pixel RGB. Watermaking is a destructive process to the image, stronger watermarks more corrupted is your original image. Watermarking is similar to jpeg compression. In jpeg compression some elements of the image are destroyed resulting in the compression of the image. In watermarking some elements are added to the image. Watermarking has the property that if a you a fragment of the image the same watermark is present in this fragment. If the fragment become too small the watermark is still present but cannot be readed or identified.

Stupidity also evolves!