"do you have to worry about the crocs moving about out of their normal habitat"?
Yes mate
There is always that risk of a croc appearing.
Especially at this time of the year.
In Litchfield Park, Salwater Crocodiles have been found lurking around the swimming holes which is many, many miles away from their coastal habitats.
It is amazing how far that they are capable of moving when such a large area is flooded.
I'm unaware of any actual croc attacks in these situations but I guess that there is always that possibility.
There have been reports in the past of people finding crocs in their backyard swimming pools.
Here is a bit of info that the Northern Territory Government has made available for the kids at school to keep them aware.
http://www.nt.gov.au/nreta/kids/project/pdf/Crocodiles.pdfMick