Sydney’s harbour is one of the best in the world. One of the best ways to explore the harbour is to use the public transport ferry system, this services all points around the harbour (and you will need an Opal Card).
Take a train to Circular Quay (or taxi if you prefer) where you will be able to see the Harbour Bridge, Opera House and harbour.
To explore the harbour take a ferry to Manly – the 30 minute trip is picturesque and once in Manly there are plenty things to do – for more details visit http://www.manlywharf.com.au/see-do/the-corso/
Alternatively you can take the ferry to Taronga Zoo where you can see many of Australia’s unique fauna – go to http://taronga.org.au/ for entry costs and other details.