The Catalinas did not take off from Perth Water, they took off from Melville Water, from near the Narrows - and always in a Sth-Westerly direction towards Fremantle.
They needed the huge area of downstream Melville Water to get airborne with their 4 ton overload of fuel.
Perth Water is the much smaller area of open water bounded by the Causeway, the Narrows bridge, South Perth, and the City.
McCormacks Catalina Airlines initially applied to use Perth Water as the takeoff/landing area. During the assessment, a local MP suggested that the area of Melville Water previously utilised by the Wartime Catalinas be used instead of Perth Water.
McCormack agreed and then changed his plans from using Perth Water to using Melville Water.
This upset the SRT (rightfully so), as the submitted plans no longer matched the modified plans - so McCormack had to resubmit his plans again.
Catalina Airlines - Cessna 208 Caravan seaplane VH-OPH could be operating from Perths Swan River from early 2014 | AviationWA
During 1943-1946, during the period of the Catalinas operations, the population of Perth was around 250,000 people. Today it's over 1.7M.
That's nearly 7 times the number of people, and those people are equipped with 10 times as many recreational water toys as the people of WW2 Perth were.
We have just about the highest population of watercraft per capita in the nation - everything from tinnies to sailing boats to monstrous cruising vessels. We have PWC on a mind-boggling scale.
We have cruise boats running Fremantle-Perth and return. None of this existed in WW2.
I don't know how all watercraft owners can be educated to understand that there will now be the equivalent of a runway in the middle of their regular boating and sailing area.
Just one dumb, thoughtless watercraft owner plowing through the LZ in his jetski/speedboat, as a Caravan touches down, will be enough to create havoc.
I haven't sighted the application for the floatplane operation, but I'm hazarding a guess the LZ will be well marked with buoys, and thus provide some warning to thoughtless watercraft owners.
The bottom line is - the SRT has always rejected floatplanes on the Swan River due to “amenity and conflict with other river and foreshore activities”.
What I am basically asking is - what has changed in the last 7 yrs for the authorities to now allow floatplanes?
The only thing that has changed is McCormack initially proposed to use his Grumman - but changed his plans again, and offered to use the smaller Caravan instead, to try and get his business plan "off the ground", so to speak.