The big shark investigated him first, then switched its attention to another cage nearby.
'You can see the diver pushing the shark away," he said.
"I even captured him with his hand in her mouth at one point. It was by far one of the most amazing experiences I have had in the ocean."
Department of Conservation shark expert Clinton Duffy said it was not unusual for sharks to "mouth" a cage to see what it was.
But it was rare for a shark to attack a cage deliberately.
In a dramatic incident near the same island a year ago, a great white was swimming to eat bait hanging in front of a cage when it overshot its goal and got stuck - giving both shark and diver a huge fright, said Mr Duffy.
"The shark gave one or two flicks of its head and the cage completely disintegrated."
But the beast was not after a meal of human. "The [diver] just swam back to the boat and got out of the water. It ended well for everybody concerned."
He said sharks would often collide with a cage when grabbing a bait.
But it was very rare for a shark to attack with the intention of reaching the person inside.
"They are usually quite cautious. But every now and again you will get one that will do something completely different."