IF YOU THINK YOU KNOW SWIMMING YOU MUST WATCH THIS VIDEO- This is Jason Lezak clocking a 46.06 relay split I personally can't believe how fast that is but here it is.
http://www.youtube.com/watch?feature=endscreen&v=sxy920Nd7yY&NR=1
By the way all of these videos aren't to promote these certain YouTubers I try to find the best quality videos for you guys. (I know this isn't the best quality but its the best I can find.)