I never used watermarks, as I find them either too intrusive or too easy to remove / crop out. Photographs at my website are low resolution (800px max), released under a Creative Commons license (free for not-commercial use, unmodified, attribution required): better ask of a "fair use" than waste my non-existing resources pursuing copyright infringements. I just sell ("try to sell" would be a more precise term) prints, not interested in digital files.
But I am just an amateur...