The horror.

This is almost as wrenching as the factoids from the Gene Weingarten article on parents who left their children in hot cars.

[O]f the approximately 750 children who will drown next year, about 375 of them will do so within 25 yards of a parent or other adult.  In ten percent of those drownings, the adult will actually watch them do it, having no idea it is happening.

Apparently this happens a lot. It almost happened to me when I was a toddler.