If I ever caught mine having an accident (in the act), then I would say "Uh-oh!" It was funny, because I can remember the exact time when I knew she understood what she had done. She stood there looking at me
while I was cleaning the floor. Yes. She was looking right in my face. Of course, I was lecturing her, too. After that time, it was a breeze. To this day, if I say "Uh-oh" for any other reason, it still gets her full attention.