[OC] Sydney CBD, Opera House and botanical gardens viewed from the harbour +2 more pics in body.
Behind the Sydney Opera House is Circular Quay, which is the hub of ferry traffic in the harbour. There's also private vessels, cruise ships, , a floating bar and the occasional military vessel.
There are several classes of ferry in the fleet, including rivercats (on the left) which have a shallow draft as they travel up the river to Paramatta.
The largest class of Sydney Ferry are the Freshwater class which travels to Manly and back near the Sydney Heads which can lead to a bumpy ride if there's a swell.