Understandable. Maybe it helps if I tell you that no one dies in the videos. They are all rescued by a lifeguard.
There is this article which describes the same content: https://slate.com/technology/2013/06/rescuing-drowning-child...
But if you just want the gist of it: Drowning people can't shout for help. They can't raise their arms and wave. They typically spread their arms forward on the surface of the water and kind of bob up and down, but their mouth and nose doesn't go above the water long enough to finish a complete breath in-out cycle.
Someone drowning isn't at all like pictured in movies. Those videos aim to dispel that, and maybe teach you some of the signs of someone drowning, and also that you should watch your kids closely when they're at the pool.