Whether it's a kid drowning in the tub in that split second when you go to answer the phone or the door, or a large-headed, top-heavy baby drowning in the toilet, the bathroom is the site of over 300 unnecessary drowning deaths each year. [Hmm. Since I can't find reliable figures for necessary drownings, maybe we'd better call them "easily preventable" instead.]
Check the CPSC tips for preventing household drowning accidents, don't leave a kid alone in the bathroom, and keep the toilet shut.
A public service announcement from the guy at Daddy Types who's had this list of people who died in the bathroom in his browser all week.