Can a water mark be erased some how by anyone and how to make it? Photo theft concerns. pls help?

The best watermark will me one that is the width or the height of the photo, but at an opacity of around 10%. This way it's faint enough to 'see through' and see the photo, but it's still distinguishable as your photo. If that makes sense.. Put your watermark in the centre of the image, and give it very low opacity. The only way someone can then get rid of it is to Photoshop the image, as you suggested, which will take some skills to be able to remove the watermark and still keep the photo/image looking original, and in some cases, will be too much work for most people.