Shonan Trader, yes it is doable in one day, it will take you just over 1.5hrs from melbourne cbd to Torquay. As you will be going against the traffic from the cbd and head out early, you could spend a couple of hours at least at torquay and then head on to the apostles and another couple of hours there and then head back and be back in melbourne by dark. Really there will be plenty of time available to spend longer.
