mineral1 said..Happens faster than one can imagine. Was with two grandchildren at a small pool in a Van park, another Dad with four kids playing in the kids pool. Came time to all head home for dinner, Dad starts with number 4 and takes his floats off. Then commences to do the same with number 3 while 1 and 2 are chatting away to Dad. Number 4 now walks to pool edge behind Dads vision, and jumps in, not a sound and swims like a rock straight to pool bottom.
My Grandson yells as he spotted the lad on bottom. Dad turns looks at Grandson, but none the wiser cant see number 4 at his feet on pool bottom and turns back to 1 and 2. Grandson all of 9 jumps in yelling at the top of his voice, Dad turns then spots good ol number 4 on pool bottom. Grabs him by an arm and hoiks him to pool edge spluttering and coughing. All this in less than 20 seconds

The Dad after the shock, came over and gave Grandson a huge bear hug, all the while telling him how good a person he was

Ol number 4 still going at full speed jumped up and also hugged Grandsons legs, not knowing then, why his good ol Dad was hugging Grandson so much.

Yes.
I know of another very similar instance.
Mum and Dad chatting by side of pool while young son at bottom of pool less than 3 metres away.
Other son runs up and tries to get mum and dads attention but is told to be quiet,. can't you see we're talking.
Eventually, and disregarding the directive, he shouts out a jumbled message which by it's urgency indicates someone is drowning.
All turned out well, including much praise for the one who ignored the message to shut up.
The BIG message is,.. when there are very young children in a pool, you have to KEEP WATCHING.
It's not much use if you are there but not watching.
Drowning with young kids is an extremely quiet process.
They just slip away in front of where your eyes should be.
If you can't watch for any reason then get them out of the pool.
No 'just ducking inside to answer the phone,..or off to the loo,.. they will be all right.'
Mostly they are but it's a dice which when rolled, can come up with some devastating consequences.