Now before anyone says that this tutorial is unethical, there are situations where removing a watermark is appropriate. For example, if you wish to remove a watermark so that you can get a better idea of how the photograph will look BEFORE you purchase it, then this would be alright. However, as a disclaimer, let me say that in no way, do I condone removing a watermark in order to steal images.
1. Open the photograph that has the watermark.
2. Select the Clone Stamp tool.
3. Zoom in to an area of the watermark. Hold down the ALT key and select an area of the photograph just to the left or right of the watermark.
4. Release the ALT key and paint over the watermark image.
5. Continue to do steps 3 and 4, working your way around the entire watermark until it is completely painted over.
6. You should now have your image without the watermark.