"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."
Stewart's friend Coralie Fleming witnessed the shark going for his foot, and thought she was seeing her friend's life being taken away in front of her eyes.
"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."
The pair, along with Fleming's boyfriend, scrambled 30m to nearby rocks before swiftly getting back to their boat where upset and shock set in.
However the trio said despite being terrified, it was a beautiful encounter.
Stewart reported soreness to his left side following his brush with the 3.5m shark.
Department of Primary Industries spokesperson Dr Vic Peddemores said the shark's behaviour indicated it was taking "a test bite" to see whether the divers were a food source.