"It's not a sensationalistic statement to say that the sharks that swim off here are very dangerous," Nyad told ABC News in July. "They're aggressive. They're curious. They for thousands of years have heard a fluttering on the surface to mean to them 'dinner bell.'"
Her team is using an electronic boom to surround Nyad with a current that will keep most sharks away.
"It's going to be a daunting task," Nyad said. "I feel confident and on the other hand I'll admit to you I feel afraid.
"When I tried to swim before in 1978, I was 28 years old. I didn't have as much fat on the body. I was faster in the water. On the other hand, at this age, I do feel a little more bullish," she said.
"I am much more in control of my emotions. I actually think I'm a better distance swimmer than I was in my 20s. In an emotional, mental sort of stance, I'm in an athletic prime even at just one month shy of 62," Nyad said.
She told ABC News that the message behind her swim was "to live your life big [and] burn the candle large.
"When I go to sleep at night, I say, 'How much more could I have put into this day?' Nothing. That's the way I want to live," she said.
The Associated Press contributed to this story.