This is a privately owned company running parallel and different routes to the government ferries.
And before anyone has a rush of blood to the head & hits the "inappropriate" button as they did on the markets thread - I have no connection with the operators! Like that poster, I am merely a local interested in telling people about things they they may not see on the normal tourist info sites.
The website is www.manlyfastferry.com.au Tel: (02) 9583 1199
They run catamarans and their routes include
Manly east pier
Q (quarantine ) station
Great service as a stand alone or in conjunction with the STA ferries.