This is of course one of several dinner cruise boats (all heavily glassed to enhance the view) which plies its trade around Sydney Harbour. (I can't recall the name of this one and it's not visible even at full size.)

A trick of perspective (to be fair, more visible in real life than it is here) made it appear that the thing was belching copious quantities of smoke behind it. The smoke was of course actually sourced from an unknown fire on the Balmain headland beyond.