One critical thing to be aware of is that someone who is truly drowning is completely silent. They aren't yelling for help, they aren't splashing around. There are zero audible clues whatsoever.

Their mouth is under the surface, so they can't yell, and all their flailing around is happening under the water's surface too...so there is no splashing or any other noise.

It's really creepy as heck.

So if you are at the pool "watching the kids" but reading a book and just glancing up every few minutes, your kid could be drowning literally within a few yards of you and you wouldn't know it.

Not to scare anyone, but something to be aware of. I got lucky that someone was looking right at my daughter (me once, her brother the other time) when she decided to jump into a pool before she knew how to swim and was able to fish her out.