Take your pick up there mate.
sharks... various
marlin
sail fish
mackerel... various
giant trevalley
reef fish various
There is a spiecies of cod up there that reach the weight of a medium sized car, but A/ you wont stop em...B/ they are protected
If you are realy game..... floating handbags have been known to put up a good fight on light tackle.
BTW...... what sort of boat will you be buying
In townsville if you don't have a boat or access to one ( of any size) you are considered either under privaledged or weird.
I hope you like the heat & humidity...... there is plenty of that up there.
But the roads are good & nowhere is very far from anywhere else.
cheers