When the white water turned red, Matthew Holmes "just knew".
Inside the 22-year-old's head there was a voice screeching loud enough to drown out the hum of his idling jetski: "Shark! Shark! Shark!"
"I turned to my mate, who was on the back of the jetski, and saw the look on his face - it had clicked with him, too," Mr Holmes said.
Mr Holmes whipped his friend into shore and headed back to the surf where Ben Linden was being mauled by a 5m great white.
Mr Holmes' repeated efforts to try to save Mr Linden on that July morning in 2012 has earned him one of Australia's highest civilian honours.
The carpenter, now 24, married and a father to an 18-month-old son, will today be revealed as one of two West Australians to get a bravery medal as part of the 39th Australian Bravery Decorations.
Previously reluctant to talk about the fatal shark attack near Wedge Island, about 160km north of Perth, Mr Holmes told The West Australian of his split-second decision to put himself in danger in an attempt to save a man he had never met.
"I saw a big splash and the tail end of what looked like a whale or a big shark land in the water, right next to these two guys," Mr Holmes said, referring to Mr Linden and one of his friends.
"I was probably 50 to 60m away. It took a couple of seconds to sink in what was happening.
"When the white water went red within a couple of seconds, I just knew."
By the time Mr Holmes got to the scene, the water was clouded by blood.
Mr Linden, 24, was face down.
The shark had let go of him, giving Mr Holmes the chance to pull him on to his jetski.
"I grabbed Ben by the back of his hair and wetsuit and tried to sling him on the back," Mr Holmes said. "There wasn't much movement . . . he didn't say anything but he wasn't dead. I was so focused on him, I wasn't worried where the shark was."
Mr Holmes said Mr Linden was out of the water "for maybe a few seconds" before the shark suddenly returned and slammed into the side of the jetski, almost tipping it over.
"The whole jetski bobbed to the side and bounced back up," he said. "I nearly fell off and wasn't able to hold on to Ben.
"The jetski basically turned 180 degrees on itself. It was such a big shark.
"I've surfed and fished my whole life and have seen sharks but there was nothing like this, nothing I've ever seen before."
Terrified that the predator would turn on him, Mr Holmes guided the jetski away before returning, only to see the shark pull Mr Linden under water.
Mr Holmes followed the shark for several minutes but never saw Mr Linden again. He grabbed Mr Linden's board, then raced to tell other surfers to get out of the water.
"A couple of the other blokes looked at me and laughed," Mr Holmes said.
"They didn't believe me until I held up the surfboard with the bite mark in it."
Mr Holmes said he had still not found the courage to go back in the surf.
"Even things like having a shower or going in the pool took me months to get my head around," he said.
"I still think about it every day. When it first happened I was a bit messed up because my wife was having our first kid. I look back and think if my little boy didn't have a dad, how would it be for him growing up."
Mr Holmes said the memory of the shark attacking the jetski haunted him. "I saw the full head, I watched it eyeball me," he said.
"That's just the image that I always see - that big eye, the thickness of the head."
Mr Holmes said Mr Linden's father and girlfriend had contacted him in the aftermath of the attack to thank him.
A coronial inquest was told last year that there was no doubt Mr Linden was killed in a "catastrophic" shark attack.