Our prayers and thoughts are with the family.....
I just thank God, that every time my kids have asked to go in a pool (our own, a hotel's, etc.) without adult supervision, i have said "no way, no how." And there have been many times, especially on vacation, when everyone is so happy and having a great time, that I have been tempted to say "Sure, go ahead, I'll be right behind you." Something always stopped me from saying this.
What a tragic loss.