Novack, 38, broke the previous record Sunday, set in 2008 by Peter Attia, by 44 minutes, and is the only woman to attempt the two-way swim, the Honolulu Star Advertiser reported Monday.
It was only after she completed the swim that she was informed by her support crew a 15-foot tiger shark accompanied her for part of the journey.
"The only thing that kept me safe was the Shark Shield," Novack said, referring to an electronic shark-deterrent device. "I'm glad they didn't tell me."
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