Steve Bruemmer, 62, was swimming off Lover's Point in Pacific Grove last week when he was savaged by the shark, with injuries to his stomach, arms and legs.
You can watch a video of the rescue below:
Bruemmer had been swimming alone when the attack occurred. But thanks to the quick actions of onlookers, he was pulled ashore by a surf instructor and two paddleboarders, who ultimately saved his life.
Miraculously, despite losing more than 25 pints of blood, doctors believe Bruemmer will make a full recovery from the injuries - which have been described as some of the worst bites ever seen.
One of the rescuers, Heath Braddock, told KSBW: "We got my biggest board and the gentleman, Paul, helped me roll the victim on the board belly down and got him kind of centered and stable. We had him hold my foot and we paddled him in."
Meanwhile, another rescuer, police officer Paul Bandy added: "He was screaming for help, you could tell the sound and the emotion in his voice that there was something definitely wrong and he was slapping the water.
"I wasn't sure if that was some sort of thing he was trying to get something away from him or just trying to draw attention to himself."
Pacific Grove Police Chief, Cathy Madalone added: "We want to express our gratitude and appreciation to the Good Samaritans that took immediate action and personal risk to assist the swimmer."
Days on from the attack, the shark has been confirmed to be a great white by the California Department of Fish and Wildlife, following a forensic examination of the bite marks on Bruemmer's body.
Experts also believe the shark could be around 20ft long - which is equal to a female great white known as Deep Blue, who is the largest great white recorded.
Deep Blue is thought to weigh 2.5 tons and is believed to be over 50 years in age.
Bruemmer remains in hospital, with what is expected to be a long recovery.
In a statement, he explained: "The shark bite was unlucky. But after that, I have just had so much good luck.
"The day was so calm and warm, and the beach was crowded. There were no waves, and there was no chop. So people could hear me yelling 'Help!' from a great distance."
Featured Image Credit: Facebook/Kevin Phillips/KSBW