The article shared by u/browncoat4life links to another piece that really surprised me. It explains that people who are drowning don’t always look like they are in trouble. I highly recommend reading it:
Drowning Doesn’t Look Like Drowning
This is an important lesson we can learn from this sad event.
When I was 14, I was doing a lifeguard course (it was in the 90’s) and the simulation of someone drowning always had the victim panicking and waving their arms all around… it was so far from reality.
Had I worked as a lifeguard, I’m not sure I would’ve spot a real victim 
…
Times have changed. My friend used to be lifeguard and when I showed her this video, she said right away he’s struggling to “break the surface”. Apparently this is essential when working in public pools.
I sincerely second this 
Lifeguarding multiple people is extraordinarily difficult, especially if they have no set task. I boat with my kids often, so I’m familiar with what drowning looks like, but I only look at two people.
Yeah. Sadly Drowning doesn’t look like it does in the movies. 
makes sense.
when i was starting with a freestyling swim course, i often joked: that’s a drowning class. i still sometimes need stop kicking (beefy fast twitch legs) because it would suck so much oxygen so that I couldn’t maintain my stroke rhythm. I guess labelling it as drowning class isn’t totally wrong: “… not using legs…”
Thanks friends atleast have known alot