As a footnote to the cat fishing scenario. Cats can and do try and fish a pond, it's their nature as a hunter. For anyone one who'se never actually seen this they will sit at the edge of the pond and if anything comes close enough will try and hook it out with their claws. Although they very rarely manage to hook a fish unless it is already injured or ill they can cause damage to the fish with their claws.
In many countries the list of wild preditors is very large and many enter natural ponds as a matter of course in search of the next meal. If they come across an ornimental garden pool they will treat it in exactly the same way.
