Watching the Olympics I have found the swimming very interesting. I've noticed that while the swimmers are swimming the TV Channel (BBC) projects a line across the width of the pool saying WR (World Record) at the end.
I'm a bit unsure about this line, I know it's to show where the swimmers would need to be at to get the World Record but is the line showing where the swimmer who holds that world record was at that point or is it showing the required place through out? e.g. say the 100m WR was 50 seconds, then the line would progress 10m every 5 seconds.