The video shows that Irwin, regarded as The Crocodile Hunter, clutched at the left side of his chest before he went into cardiac arrest.
"It was not that obvious," news.com.au quoted skipper Pete West, who was at the scene and is one of only a select few who has viewed the footage, as saying.
"The footage shows him swimming in the water, the ray stopped and turned and that was it. If it hit him anywhere else we would not be talking about a fatality," said West, owner of the support vessel Deepstar.
The tragedy struck when Irwin was shooting the documentary Deadly Sea Creatures on Batt Reef. He was pulled from the water by the cameraman and a member of the crew, and taken to the Deepstar about 500m away.
"I could see Steve slumped in the arms of his other crew member," West said.
"The driver told me Steve had been ' hit by a stingray'. It didn't take any time for me to realise the seriousness of the situation. The vicinity of the wound, the amount of blood he had already lost and the apparent lack of vital signs," he added.
West, an underwater cameraman, returned to Batt Reef on Monday night to pay quiet homage to the memory of Irwin, and to film the big bull rays that claimed his life.
"Like so many I was one who didn't truly appreciate the significance of Steve and his work until it was too late. Until Steve's death we paid little attention to stingrays. There are many species at Batt Reef some nearly 2 metres in diameter and weighing in excess of 200kg," he said.
"With each encounter we learn more about this amazing animal and there is no doubt - we now treat this normally docile giant with the same respect once reserved for dangerous marine animals," he added.