To be fair, you don’t need to knock them unconscious, you just wait until they fall unconscious on their own from the whole “drowning” part. At least that’s what they taught us to do if it was too dangerous to approach someone. A lot of the rescue techniques where also specifically designed to grab people from behind/immobilize their arms for similar reasons.

Also I’ll never forget the instruction that if someone panicking / drowning does grab onto you to try to keep their head under water, don’t fight them and try to get to the surface. Instead stay calm and go down once holding onto you means going underwater, they’ll let go.

And as always 1) Reach (ie grab someone from a safe location/ reach out to them with something inflatable that they can latch onto) 2) Row (approach in a boat, particularly in open water) 3) Throw (an inflation device) THEN 4) Go

Going into the water after someone is dangerous and other options should be considered first, even for lifeguards. As a bystander, your first instinct may be to jump right in, but always look for other options.