> In this case the advice is good and worth keeping in mind
How do you know? You can find a population on the Internet that will tell you almost anything is a good idea, especially groups of people in the same online community. Anti-vaxxers come to mind.
I can't speak for him but in my case I know that advice is good because it's an accurate summary of what I was taught in a Red Cross certification course. I can't prove that to you so your epistemological objection still stands, but if you're actually curious you can download the American Red Cross lifeguard manual here: https://www.redcross.org/take-a-class/lifeguarding/lifeguard...
Reading that manual is not a substitute for actual lifeguard training, but I expect you'll find it supports the general points made above.
Specifically pages 161 and 198 confirm the advice "If they get hold of you, DIVE so they let go." In my personal opinion that's the most important advice in that comment since failing to free oneself from a drowning victim is the cause of many multiple-drownings. The Red Cross goes into specifics on how exactly you do it, and when you're receiving training you practice doing it with the other students or instructors, but that short summary is an accurate summary.
Because it's a subject I have knowledge of and the given information is an accurate summary of some of that knowledge?
Facts aren't just floating out there in the aether, many of them are testable. There are also people on the internet who well tell you that vaccinations are helpful. Oh my gosh, how do you even know the truth on this crazy contraption? It's shocking that this problem of determining truth is entirely and wholly isolated to this one communications medium and no others isn't it?
I guess you could always just wait for something on television to tell you the absolute truth.
How do you know? You can find a population on the Internet that will tell you almost anything is a good idea, especially groups of people in the same online community. Anti-vaxxers come to mind.