Along with being unlawful, cutting out a photographer's watermark is just down right rude. A watermark is how they get recognition for and claim ownership of their work.
Cutting ouf a watermark is denying the photographer the recognition they deserve. Imagine if your favorite photographers started cutting off your face and just showed your costume? Probably time to find some new photographers or a new hobby, right?
Thinking, "Well, I'll just give them credit elsewhere on the page" doesn't work. The moment somebody else takes the photo from your site, that information would be lost.
It is also the artist or phographer's right to decide how, where and what information they wish to display, so don't make editorial and artistic decisions to suit your own needs. Adding additional watermarks that imply or confuse copyright ownership is also wrong.