I mean surely you can tell you're a fast swimmer. You are overtaking lots of people, getting in their way and you are going the same speed as people who are in the fast lane.
Had a swimmer who insisted on just using the Medium speed lane, but instead of swimming anti clockwise like everyone else, he just decided to go up and down in the middle - so as to dodge the people swimming at medium speed.
I was so tempted to say something. Is there such a thing as swimming rage?