Back when my son was three(he is six now), he would go out and play with his sister and his aunt and uncle (long story, they are the same age as my kids, they also live on the same compound). They play all day long, horses, dogs, cats, a play fort in the back the size of a small house.
They come in for dinner, all except billy, they hadn't seen him for an hour or so, so I go outside to look for him, and the first thing I see is his life jacket floating in the middle of our lake (about a 14 acre lake).
I nearly crap myself with fear, yell for my wife and the nanny, my father and his wife and the bunch of us are in the lake diving around trying to get to the bottom of this lake (about 25 feet deep).
This goes on for about 5 minutes, with the whole crowd getting more and more desperate, my wife and I are both in tears as we are diving under the water, when what do we see, billy at the top of the fort, watching us with much interest.
It's funny, the kids know not to go in the water, and all of them said that they hadn't gone into the water, but one look at the life jacket and I *knew* he was in the water, he wasn't. He had fallen asleep in the castle.
Needless to say, lots of upset.