I view lifeguards as similar to the Police. They are nice to have around and can certainly be a great help when there's trouble, but they are not personal bodyguards.

When my family is swimming, I'm constantly counting heads, keeping track of my own kids. Lifeguards can't keep track of who's in or out of the water and know when someone is missing.

I've seen guards do a search of the water in a lake swimming area several times, once was a drill and the other was a false alarm. They line up shoulder to shoulder and sweep parallel to the shore line, starting at the shore and working their way out in successive passes. When they reach deep water, they dive, swim along the bottom, back up a bit and repeat. It struck me that unless there was a point last seen to start searching from, the real thing would most likely be a body recovery.