In zoos it seems to me to be especially common in goldfish and koi ponds and crocodilian exhibits. At least in the zoos I know I've seen the phenomenon decline in pinnipeds pools luckily, perhaps due to information given, but I'm sure it unfortunately still happens sometimes.
Again speaking about my visit to Pairi Daiza today: another thing that really annoyed me was the behavior of quite a few people on the lemur island (ring-tailed, red ruffed and black-and-white ruffed lemurs): touching and petting the lemurs, instigating their children to do and trying to get lemurs to sit to them to get interesting photos/selfies. There are signs clearly saying it should not be and unfortunately there wasn't enough supervision (and a lot of people also). This is one of the reasons why I'm not a huge fan of walk-through primate exhibits, even if they might admittedly be nice for photos...