Hi, I've applied to Syd University, and because I live quite far from the university, I was thinking about staying at a residential college...
I applied for John's, Andrews's and Wesley for 2015 and received offers from both John's and Wesley. I can't speak for Paul's, however IMAO to be accepted it's a bit of a see-saw between academics and extra curricular activities as to whether you are accepted (excellent extra curricular allows you to get in with lower HSC/ATAR results and vice versa.)
However, I don't think playing sport in 2015 will particularly help you extra curricular wise as you are going up against stacks of people who are state or even national athletes. However, it will help you in that you can push forward that you thoroughly enjoy sport etc. Also if you haven't done any sport before that section of your application will look quite poor.
So I would recommend doing the sport if you don't have anything before but don't let it chunk up too much time. Maybe check out some fun runs. Also look at the nsw all schools team triathlon - sounds almost as good as individual but requires a lot less training, you could even do no training and just participate.