Join Date: May 2006
Location: New York, London, Sydney
Programs: United GS/2MM, DL*P, VS*G, AA*EXP, Avis CHM, Hertz Platinum, Sixt*D, HH*D, HGP*P, Starwood*P
Posts: 9,877
Canberra? Seriously, mate? When the OP asked for a beach locale? Okay...
Seriously though the best beaches you're going to find will be right in Sydney. If you want more low-key, head up to Port Stephens (Shoal Bay is a personal favourite)---about two hours from the city (less than three) and very nice beaches, very low key.
In Sydney head to Bondi (okay, I'm partial, but Bondi rocks) or to Manly. People will tell you to head to the Northern beaches for more low-key, I prefer the ones closer to the city, YMMV.
PM me if you want more info.