As I mentioned in another comment, SEQ waterways are full of bullsharks - so you're 100% correct. That doesn't make the story true.

The photo is from Wikipedia - it has nothing to do with the report.

There are no crocs in the Brisbane river. Bull sharks are common in waterways in Southeast Queensland. This could have been real, or not. I'm leaning towards not because it is just one person who though they saw something in some pretty messy waters.

Except that it's just his word with no evidence - that'd be one reason not to believe him.

It's hard to describe just how much junk was flowing through the flood waters last week. This really could have been anything.

So one person reports (unconfirmed) two bull sharks in flood waters. Local media the next day generally has the opinion the story is a load of bollocks and now almost a week later it appears on Slashdot (a news for nerds site) as fact.... OK.

If you want some (slightly) more nerdy stuff to report about the floods go research the Wivenhoe dam.

I've really got to stop reading idle stories.