Answer
Walter Poenisch and Susie Maroney were the two other people known to have completed the Florida Straits crossing before Diana Nyad. Poenisch, a native of Austria, made the crossing in 1978, while Maroney, an American, completed the swim in 1987. Nyad, a native of New York, made the crossing in 2013, becoming the first person to do so without the use of a shark cage.