That's a thumper
i caught one that size when fishing off the back of a moored boat at lake macquarie, had it in the keeper net for 1hr (i keep checking because i couldnt believe the size) and then decieded to go back into shore, pulled up the keeper net and it was gone , somewhere in between me checking the net and three minutes later it was gone!
but i showed every1 from shore and i did get a chance to measure it so it was better than getting it to the boat and then it getting away.