Interesting to read the comments quoted by Mack McCormack in the post from the Daily Telegraph. He is the owner of the Grumman Albatross VH-NMO, that he had spent months trying to get through the red tape to operate in WA. He actually moved the aircraft to the eastern states on 22nd December 2016, after giving up trying to get approval.
Not sure if Mack is endorsed on seaplanes, but I used to go to work in the South China Sea on his aircraft when it operated out of Singapore back in the 1980s. It was flown by friend and legendary seaplane pilot
Bryan McCook(RIP). The Albatross is a bigger version of the Mallard.
I am a former helicopter pilot and used to always ride in the jump seat with Bryan, and even with his vast experience it was obvious that those aircraft are unforgiving, and in old parlance a "handful", especially on approach and water landing.
RIP to those lost, and I hope that some good comes out of this tragic event, that as with many accidents, it was the culmination of a series of small mistakes that should have been avoided.