Kittens and water butts

We had a phone call from my sister to say that the kittens' sister, who had gone to another family, had drowned in a water butt. (Our water butts do all have lids, and we've now double checked they are all on reasonably securely, but we did have a squirrel drown in one a while back. The drowned bat was in a bucket with no lid, but a kitten could climb out of that, unlike a deep butt with overhanging sides.) This has been a public service announcement.