There were seals in the water as Callum Stewart made his way to the surface off Martin Island about 9am Saturday. He was five metres below when he thought he felt one of them bump him from behind.

The blow knocked him upward. Something brushed against his left arm and he marvelled at the seal’s incredible power and bravado. Through a curtain of bubbles, he was awestruck to realise his error. 

“I turned around to have a look and that's when I saw it was a shark,” said Mr Stewart.

“It did a full 180-degree turn and came back to look at me. That's probably the point I realised I might be in trouble. 

“The most amazing memory I have is looking this thing dead in the eye, and wondering if that was the last thing I’m going to see. 

“I was kind of caught up in the beauty of it.

“I realised later, it had my fin in its mouth.”

Mr Stewart, a 28-year-old engineer, says he never felt his fin, measuring almost a metre long, pulled off. However his diving companion Coralie Fleming saw the moment it left his foot. 

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For a split second, she thought she was seeing her friend pulled in two, Ms Fleming said. 

“It [the shark] opened its massive mouth and as it’s closed its mouth it kind of ripped down as it went to swim away,” she said. “There was one metre [missing] off Callum’s body. I was horrified, then I realised it was just the fin.” 

“We’re just lucky that it was an investigatory bite and didn’t involve any missing limbs.” 

“Once we got back on the boat I was pretty upset and a little bit shocked, but it’s a really beautiful encounter with out of our most revered apex predator. It’s this really weird combination of being terrified, but also completely in awe.” 

The encounter was caught on camera by Ms Fleming’s boyfriend, Mitchell Scanlan-Bloor, only a few minutes after the trio entered the water. 

With their boat 30 metres away, having dropped anchor, they scrambled onto nearer rocks to make the quickest possible exit from the water. 

Ms Fleming lost her own fins to the sea in her frantic struggle to get ashore. 

Mr Scanlan-Bloor was first out of the water, then stopped to pull the others in against a big swell. 

“We copped a real beating on the rocks but were out of the water within a minute,” he said.  

Dr Vic Peddemors, the Department of Primary Industries’ head shark researcher, said swimming in the presence of seals increased the likelihood of an encounter with a large shark. 

“But that said, there are hundreds of people who dive with seals and rarely do they encounter a shark, let along have an incident where the shark interacts with them,” he said. 

Dr Peddemors said the shark’s described behavior indicated it was taking “a test bite”, to determine whether the divers were a food source. 

“I didn’t get the impression it came hurtling at Callum,” he said. 

“If it had, it would have pushed him right out of the water with a shark of that size, and it wouldn’t have just been his fin that was missing.” 

The department encourages the use of its shark smart app, which collates historic and other data to determine the risk of a shark encounter. 

Mr Stewart reported soreness to his left side in the aftermath of the encounter, and attributes a bruise on his buttock to the initial blow he received. 

Other injuries, including scrapes that caused punctures to his wetsuit, may be the result of his scramble onto rocks, he says.