I believe one person who has flown under the Sydney Harbour Bridge is Sydney businessman Phil Dulhunty. He had told me had done it once but in his own words he has done it half a dozen times.
Phil was one time chairman of the Seaplane Pilots Association and the association's newsletter of 2009 has some recollection
http://www.seaplanes.org.au/Newslett...20-Aug09-f.pdf
Phil is now 91 but for many years has been actively involved in securing and returning a Catalina to the air. He is currently (and still) the Chairman of the Catalina Flying Memorial. They found and purchased one in Portugal, returned it to Australia and now doing the hard bits in funding its restoration to fly again.
About Catalina Flying Memorial