Hey JBA,
I live in southern sydney and there are a few places to ride around here. Depending on what you want you have a few options. Brighton & Dolls Point are both spots with flatwater kiting and they're close to the city (15-20 minutes). Cronulla has waves, and is around 30-40 minutes from the city, and Kurnell is another flatwater spot about 10 minutes out from Cronulla. We have an oil refinery, power station, poo plant, tip, sandmining and we may soon have a desalination plant

. So we've got everything here out at Kurnell.
Water temp gets down to about 15C at its coldest in winter, and up to 22-23C in summer, with air temps around 15C in winter and 30-40C in summer. It's a nice place to live though. Ask anybody who lives in the Shire and they'll all agree it's a great place to live. Northern beaches look nice too but the traffic turns me off up there. It takes about 10 minutes to drive down the street. Plus I heard the guys up there don't shower either