When In was younger, we had 2 cats & my father had a big fish tank in the sitting room. One day he was cleaning the fish tank. I'm not totally sure how, but our big (he was choncky) orange cat (sisters cat) fell into the fish tank!!!!! He was ok, although he did get everywhere soaking wet, as was he of course

I think the fish were ok.
Another time, my cat, a calico, was looking into the pond in our garden which had fish in it. Both loved to do that & they just watched, no fish harmed. But somehow she just slipped and fell into the pond! Again she was fine & got out herself, just soaking wet and embarrassed. It was funny timing bc both me and my sister were watching her from the kitchen when it happened

I wonder if that happened more while we weren't looking.