Roughly 20 miles, 11 hours and one close encounter with a tiger shark after she departed, marathon swimmer Meredith Novack returned to the Kahale­pa­laoa southeastern shoreline of Lanai on Sunday as the fastest human ever to swim both ways across the Auau Channel.

Novack, 38, completed the Herculean swim from Lanai to Maui and back in just 11 hours and one minute, shattering the previous rec­ord of 11:45 set by Peter Attia in 2008. Novack is also the only woman to complete the two-way swim.

Hours after completing the difficult journey, Novack, a former U.S. Masters national champion in the open-water 3K, was still absorbing the significance of what she had accomplished.

"I’m overwhelmed," Novack said by telephone. "I did this swim to show people that when you are going through adversity, it’s important to keep believing in yourself and keep going."

Novack, a Florida native and Oahu resident, trained for 10 months to prepare for her first-ever attempt at crossing the channel.

It wasn’t until after she had completed the swim that her support crew told her that she had spent part of her journey in the company of a 15-foot tiger shark.

"The only thing that kept me safe was the Shark Shield (an electronic shark-deterrent device)," Novack said. "I’m glad they didn’t tell me."

Novack’s historic swim was recorded by the Surf Channel for future broadcast.