How about this...
Being involved in a sport can teach you many things: how to work as a team, leadership, responsibility, humility and sportsmanship. However, I never thought it would teach me to appreciate the environment. As a member of the Varsity Crew team for four years I learned all this and more. College athletes are forced to learn time management and responsibility in order to achieve success on and off the playing field, all the while developing team and leadership skills. In my experience I also learned that the very water I glided on day after day is constantly in danger. I never thought my membership on the crew team would inspire me to persue environmental law, but that is indeed what happened.
This is my rough first thoughts, but you could then go on to describe anything more detailed about why being on the water lead you to persue environment law. Did you see polluting or something that worried you?
I talked about my experience in college sports defining my character in my PS and I think it turned out nicely. This is just an added dimension of this because there is so much character building in sports I think, and then you managed to find something connected to the law because of your participation and love for a sport. Definitely build on this, I like it!