Thanks for posting. I was a lifeguard for six summers & had to be prepared to spot the person quietly in trouble in a large pool full of thrashing kids.
There were lifeguards that were more concerned with their tan - it always amazed me why really bad things didn't happen more often.
Years ago we took the kids to a big water park. I observed quiet a few (many) people who could not swim, go onto slides that ended in deep pools. Each would begin to drown and a lifeguard would pull them out.
These sinkers would then race to the next slide down the line and repeat process for another lifeguard. The lifeguards at each pool were doing a save almost every 5-7 minutes.