A 31-year-old becomes first known woman to complete a 37-mile swim around New York City's Staten Island

• Leslie Hamilton, 31, took to the New York Harbor to swim 37 miles around Staten Island.
• The record-setting swim took Hamilton over 14 hours, WNBC-TV reported.

Distance swimmers – insanely competitive or just a bit insane?

That's the question New Yorkers chew on upon finding out that marathon swimmer Leslie Hamilton willingly took to the New York Harbor to swim 37 miles around Staten Island.

"People were like 'Oh she must have a third arm or three eyes.' I was actually completely fine. I didn't feel sick after the swim," 31-year-old Hamilton told WNBC-TV. "I made sure my tetanus shot was current."

The athlete did not immediately respond to Insider's request for comment.

Hamilton made history with her late-night July 9 swim, becoming the first woman to complete the first officially documented swim around the island, according to WNBC.

Ahead of her 14.5-hour swim, Hamilton told WNBC she worried about the unpredictable currents of the four bodies of water she'd encounter, as well as boat traffic.

"I thought about sharks for a minute," Hamilton told WNBC, adding she and her fiancé "weren't really sure it was feasible" to achieve the swim.

Hamilton's fiancé, Yan Fu, usually guides boats around Hamilton as she swims and said he had encountered people who couldn't believe what his bride-to-be was attempting, WNBC reported.

"These fishermen were nearby, and when we told them what she was doing they said, 'Is she freakin' crazy?! What is she doing?!'" Fu told WNBC.

The athlete trained for over a year leading up to the swim, training with a local distance swimming group.

"I can only have one swimsuit, one cap, and one pair of goggles," Hamilton told WNBC. "When I needed to eat every 30 minutes, I would take carb powder which was in my water bottle, I had rollups of ham."

New York Harbor, once a giant sewer, has gone through decades of restoration and recovery, making it cleaner "now than at any time in the last 100 years," according to the city's Department of Environmental Protection.

However, the harbor is typically "not considered a swimmable portion of the river," according to The New York Times.