Why do you want to watermark you're photos? Smugmug let's you disable downloading and printing, so your photos are relatively safe from theft and that's why most people watermark them. What you create is yours and the law doesn't require you to mark it as such. I have "copyright drshearon all rights reserved" with the creation year in the EXIF data of all my photos and that's all I feel I need.
If I were to share a file with a client I would plant the word PROOF in large type across the lower center of it. Artsy little watermarks are easy to crop off.
Some people like it as advertising or a badge of ownership, but I just find them distracting.
Dale