Brisbane has many ferries and a few city-cats which are catermeran things that go really fast :-)
many brisbane people use these to simply get from one place to another....
instead of spending a fortune on a chartered boat tour or something like that, you can get a simple round trip on the ferry for a lot cheaper, and information places around the city usually have a handy little booklet with some main points of the trip, and information about it.
By ferry, a great way to get to work but an even better way of seeing the city from the river, catch a city cat with an all day ticket and you can travel from brisbane from one end of the river to the other
With the City Cat you are going partly up and down the river. If you feel like it, you hop on and off the boat. This is a good way to see more parts of Brisbane.