A grandmother recently completed a historic, 17-hour-long swim through shark-inhabited waters off the Northern California coast – all without a wetsuit.

Swimmer extraordinaire Amy Appelhans Gubser, 55, completed the aquatic journey on May 11. She began at San Francisco's Golden Gate Bridge at around 3:27 a.m. and ended up at the Farallon Islands at around 8:30 p.m. that night.

According to the Marathon Swimmers Foundation, Gubser is the only swimmer to complete that specific route without a wetsuit. Two men successfully completed the swim in 2014, and there were also three documented failures between 2012 and 2015.

The Pacifica, California, resident told Fox News Digital that she swam along intense fog in the Pacific Ocean, which she described as a "sensory deprivation bubble." 

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"I had a thought bubble around me that only allowed us to see 100 meters in any direction," she explained. "And then the water had red tide, so I couldn't see past my fingertips."

"⁠For 17 hours, I had no idea where I was, what was going on…I went into a meditative state.," she explained. "There were some 30 minute time intervals that passed very quickly. Others seemed like they were 300 hours."

The swimmer was not allowed to touch the boat on the journey, but had teammates who periodically fed her hot chocolate, chicken broth and canned peaches to keep her energy up.

Gubser also confirmed that the waters were shark-inhabited, but she kept a cool head during the trek. She suffered a few jellyfish stings, but her helpers watched out for sharks and seals.

"I really had to be very thoughtful and careful about how I approached this swim because of the sharks," she explained. "And April, May, June is when a very big migration of great white sharks takes place away from the Farallon Islands. That's why the swim has to take place during that timeframe."

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Gubser, who works as a fetal cardiology nurse at the UCSF Benioff Children’s Hospital in San Francisco, told Fox News Digital that she swam competitively in college. But she didn't pick up the hobby again until five years ago.

"I swam through college right after college, hung up my suit, and I did not touch the water for 24 years," she said. "Ten years ago, I went back in the water with a friend of mine who challenged me to go in…it was 52 degrees, no wetsuit, in February."

"I thought it was the craziest thing I could possibly do. I cried, I had a panic attack…[but] within 15 minutes, my body got this warmth that you generate from moving. And every cell in my body became alive."

Gubser sacrificed warmth and the ability to easily float by not having a wetsuit. The waters got as cold as 46 degrees Fahrenheit.

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"Wetsuits are a great piece of equipment, especially for people that are starting out in open water," Gubser explained. "But I follow the Marathon Swim Federation rules and the open water swim world rules that, for the last 150 years, have been the same. Which is a swimsuit, a cap, some form of goggles, earplugs and a nose clip."

"When you wear a wetsuit your skin rubs against the material," Gubser added. "And the last thing that I really wanted was for my skin to bleed near a shark island."

Gubser also told Fox that her newfound fame came unexpectedly. Her family is thankful that the swim is over.

"My whole family is so relieved, because I have been talking about this thing for five years, and my husband will be the first to tell you he's just grateful it's done," she said. 

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Gubser's grandchildren are too young to grasp the magnitude of her historic swim, but she predicts her achievement will become a piece of family lore down the line.

"My grandkids are so young…My two-year-old, she just swims in the bathtub with her goggles on and thinks she swam as far. Which is lovely, I love that," she laughed.

"I'm just grateful that I can give them a good legacy in the future of, you know, ‘Your grandma did that’."

The nurse also said she is overjoyed at the positive response she has received, and hopes her story inspires others to achieve their fitness goals – regardless of age or physical condition.

"I hope this story inspires somebody to not be challenged by a number [like] their age or their weight. I mean, all of my body got me across that. That's pretty impressive," she said.

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