More than 30 years after her last big swim, Diana Nyad is back in the water off Key West.  Nyad, a former commentator for NPR’s Morning Edition, became well known in the 1970s for her swim around Manhattan Island and, a few years later, for swimming from the Bahamas to Florida.

Now, at age 61, she’ll soon be attempting a 103-mile swim from Cuba to Key West. She has been training relentlessly — with 9-hour, 15-hour, even a 24-hour swim.

And she’ll be doing it without a shark cage. Instead, an electronic shark-deterrent device called Shark Shield, which works by affecting the electro sensory system sharks use to detect bioelectric fields given off by living tissue, will accompany the marathon swimmer.