Police are examining a decapitated crocodile in far north Queensland to try and figure out who hacked its head off.
Charter boat fisherman Jim Millar says he was shocked and disgusted when he found the headless croc in a Cairns waterway last weekend.
"It was disbelief at first," he told AAP.
"I thought its mouth was open because it was just white, but actually there was no mouth there at all."
Mr Millar said tourists on his fishing boat had excitedly pointed out the croc before realising its head was missing.
"They were disgusted," he said.
"These people have come to our beautiful city and one of their memories is going to be this horrible act that someone has committed."
He said the croc attack has left him feeling sick and also sad that he won't see his "mate" in the waterway anymore.
He had seen the croc most weeks since he began operating Gone Fishing Cairns about 11 years ago.
"It's not aggressive at all. It would come up to the side of the boat," he said.
"It was a big draw card (for tourists)."
A group of locals are likely responsible for the attack, Mr Millar said.
"They're probably trophy hunters and probably don't like crocodiles," he said.
"They rot the meat off it and put the skull on their mantelpiece or bar at home and say: `Look at me, I'm a great white hunter'."
Queensland Environment Minister Andrew Powell says his department is investigating the matter.
He has also sought advice from the newly-formed far north Queensland crocodile squad, which helps in the removal of dangerous crocs in the region.
"It is not safe or appropriate for anyone to take part in this sort of behaviour," he said.
Queensland police have removed the croc's remains and are examining it.
The maximum penalty for deliberately killing or injuring a protected crocodile is $24,750.
