WATCH: Surfer suffers terrifying wipeout at Jaws Big Wave Championships in Hawaii
Competing in the heats and with waves reaching in excess of 30ft, Mitchell found himself at the top of a massive barrel.
Unable to remain stable, the 42-year-old was hurtled terrifyingly off his board, crashing way down into the water.
“Free falling at Jaws,” wrote event organizers as they shared the scary clip on social media.
“Wow, it looked like he put all the pieces together fine, but when Pe’ahi decides to want to throw you over and out over the lip, there’s not much you can do about it,” the commentator said.
“Ah, man, think about your neck,” a colleague added.
Mitchell somehow recovered to have another run, but failed to get beyond the first heat at an event eventually won by local surfer Billy Kemper.
Mitchell later shared an image of the wipeout on his Instagram page, explaining just how terrifying the incident had been.
“Just want to say thank you to everyone for the txts and msgs too see if I’m ok," the Aussie veteran wrote.
“This photo is not how i envisioned my day going. I was 100% ready and really thought today was going to be special for me. But Mother Nature had other ideas.
“I will say it was my worst wipeout ever hands down today. I hit so hard when I fell I’m not sure if I blacked out or not but I remember getting sucked over then was instantly on the bottom and pinned to the rocks on my back.
“There was so much intensity down there I don’t even know how to explain it but thank god it finally let me up and I hit the surface with a sec to spare before the next one mowed me.
“I was seeing stars and not really with it after that. I tried to go back out and get back into the heat but was really just a passenger as you saw when I fell on my 2nd wave which I should of made .
"But I couldn’t see straight and my balance was off. So not the day I wanted but shit happens," he added.
The Hawaiian venue Pe'ahi is legendary among surfers for its mammoth swells, with waves reaching over 60ft (18 meters) from December to March.