"To walk away from a shark attack with not a scratch on you, it's a miracle, really," the three-time world champion, 34, said at a press conference, reports The Sydney Morning Herald.
"I'm doing okay, I haven't got a scratch on me," he said. "It's more of an emotional, mental trauma right now. It'll probably take a couple of weeks or months to get over. I don't know."
Fanning said he was mostly looking forward to giving his mom a big hug.
He also rejected the suggestion that he was a hero in any way, saying he was acting on instinct: "I don't know whether I punched it hard or just a couple of baby punches, but I just went into fight or flight, really."
A fellow Australian surfer, Julian Wilson, was in the water not far from Fanning, and described the horror of seeing the attack happen.
"At first I was frozen," he said. "Mick was looking at me, a big old fish popped up behind him. It was a lot bigger than him. I saw him start to get kind of manhandled by the shark, and I was kind of freaking out.
"He was kind of getting wrestled off his board, and then a wave came between us and I started paddling for him, just fearing for his life."
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Shortly after the attack, Fanning described it in some detail. "I was just about to start moving and then I felt something grab [and] get stuck in my leg rope," he said. "And I instantly just jumped away and it just kept coming at my board. I just started kicking and screaming."
Fanning was competing against Wilson in the final of the J-Bay Open. The World Surf League called off the tournament after the attack, and Fanning and Wilson will split the prize money.