Yusra Mardini, swimming for the Refugee Olympic Team, competes in a women's 100m butterfly heat during the swimming competitions at the 2016 Summer Olympics, Saturday, Aug. 6, 2016, in Rio de Janeiro, Brazil. (AP Photo/Michael Sohn)
TYR Performance Swimwear by Filtre Studio at Coroflot.com
In this Aug. 14, 2008 file photo, United States' Michael Phelps swims in a men's 100-meter butterfly heat during the swimming competitions in the National Aquatics Center at the Beijing 2008 Olympics in Beijing.
Michael Phelps and Ryan Lochte dive off the starting blocks at the start of the championship final heat of the Men's 400 m Individual Medely during the 2012 U.S. Olympic Swimming Team Trials at CenturyLink Center on June 25, 2012 in Omaha, Nebraska.
Butterfly Sets How to Dominate Your 100m Butterfly