There is nothing mystical or unknown about what happens when you drown. Your "one hour" number above is some kind of nonsense or old wives tale. (It could also be that someone was in the water -- not underwater -- for an hour, and the advice was to not bother trying to revive them.) The main problem is that your brain starts dying pretty quickly. After that, you're going to also have a (quite likely fatal) heart attack. This all happens within a few minutes, not an hour.
Your brain starts dying about one minute after you drown, and after 3 minutes you're probably going to have permanent brain damage. After 5 or 6 minutes, it's unlikely your brain will still work at all. The current record for survival is abut 8 minutes (female) and 11 minutes (male). That's with brain damage, though.
When you revive someone who was drowned for over 3 minutes, they're going to have very serious permanent brain damage.
Are you just making up numbers? You speak with confidence but your numbers make no sense. 3 minutes? I can hold my breath for 3 minutes but you claim that causes permanent brain damage. You also claim the "record" for survival is 8/11 minutes but there are hundreds or thousands of cases where victims survived without air for longer than that. Heck, the world record for holding your breath is 11:35. Here's a case where 7 teenagers drowned and were resuscitated up to SIX HOURS later, quite a bit longer than the "records" you claim.
To sum up, don't just make shit up on the internet, it's too easy to fact check. If you don't know then don't act like you know.