An amateur fisherman caught an ultra-rare sawfish in a popular tourist spot in the UK.

Gary Cooper was having trouble catching live bait so he decided to use a dead archer fish he found rotting in the sand at Four Mile Beach. Before he knew it, he hooked a giant mysterious-looking creature.

"When I actually first hooked into it, I had no idea what I had hooked into,'' Cooper told the Carins Post. "This thing pulled me like three miles down the beach, for over two hours. When I finally reeled it in, I was like 'what the f**k is that?"

The massive marine creature turned out to be a critically endangered green sawfish. Cooper's catch was 13 feet long. 

Scientists tell the Carins Post that the rare sawfish can grow to be more than 22 feet long, but there isn't much other information known about the fish.

Cooper was aware that most sawfish are rare, so he removed his hook carefully.

"It was pretty hard work, particularly trying to untangle the line and get the hook out,'' Cooper told the Carins Post. "With that big saw thing, it's like eight feet long and it was swinging around my legs. I actually managed to get the hook out and released it."

Cooper reported the catch to the Great Barrier Reef Marine Park Authority.

The Federal Department of Enviornment's records show that green sawfish are usually reported in the coastal waters off Broome, around Northern Australia, and down the east coast as far as Jervis Bay, NSW.

Cooper's catch was regarded as an impressive discovery to marine experts.

"It's a very significant find. I haven't heard of a green sawfish sighting in probably a couple of years now, so they're quite rare,'' Dr. Andrew Chin, a James Cook University fisheries researcher, told Carnins Post. "It's really great to see that a really large, mature green sawfish is still around, swimming out there."

"I've never seen one."