So long story short, brother in law and family at my house over the weekend swimming. His daughter who relies on floaties was in attendance. The men who were in the pool were shooting hoops. The daughter in question took off her floaties and got into pool on large first step. Nobody noticed including women who were siting right there by pool edge. A few seconds later she stepped off third step into 3' deep water. I'm shooting hoops and see head bobing in shallow end, I'm 10' away with the father. Hair color matches my daughter who can swim, so at first I'm like that's my daughter, then for some reason I say out Loud "who is that?" And at the same time realize it is the one who can't swim. I react without answering my spoken question and dive to her and lift as much as I can but I'm horizontal in the water so I lift and she goes up but I go down. The father reacts when he sees me dive and it ends up being a handoff. All parties play it down, but it was seconds away from being a CPR situation, one breath underwater and it would have been different. The story we read and is often posted about drowning doesn't sound like drowning is in my opinion true, and having read it probably spawned my reaction. In hindsight I just think how important it is to be ever vigilant in watching those that can't swim, we thought by being in the pool, with others watching, we were being vigilant, but we weren't. Seconds matter and luckily they were on our side.