Walker, from New Zealand, has been a fisherman for over 35 years. He was in the Coral Sea off the coast of Australia when he pulled the swordfish and marlin on board. In a video of the blue marlin posted to Facebook, Walker examined the carcass looking at its injuries and discussing what could have caused them.

"We've had some really weird stuff going on with predation on our fish," he said. "That's not a shark. That's not a shark bite. You can see it's sucked on the fin." Further down the body, Walker shows how the marlin has been scratched, with other "weird" injuries highlighted.