Used to be a lifeguard years ago, luckily I never had to save anyone. One thing that the article doesn't mention, but it really should, is that people shouldn't swim out and try and grab a drowning person. The drowning person will likely overwhelm the attempted rescuer, and very possibly take both people down.
If you do get in this situation and are in danger of being drowned, swim down and they will let go.

Best thing, is to have a floatation device with a rope, and throw it to/past the person, use the rope to pull it to them. If there isn't one with a rope, swim out with what you have, and keep it between you and the victim. Hand it to them, but don't let them get close enough to you to grab on.