Natalie Coughlin of the U.S., has already had quite the Olympic career. If she can win two more medals in London, she'll be the most decorated female swimmer in U.S. history. (AP Photo/Kathy Willens)

Gold medalist Natalie Coughlin of the U.S. shows her medal after winning the 100m backstroke the 2004 Olympic Games, August 16 2004 in Athens, Greece. (AP Photo/Mark J. Terrill)

The United States 4 x 200-meter relay including Carly Piper, left, Natalie Coughlin, and Dana Vollmer, celebrate after winning the gold medal in a world record time 7:53.42 at the Olympic Aquatic Centre during the 2004 Olympic Games in Athens. (AP Photo/Mark Baker)

The United States 4 x 100 freestyle relay team from left; Kara Lynn Joyce, Jenny Thompson, Natalie Coughlin, and Amanda Weir diplay their silver medals at the Olympic Aquatic Centre during the 2004 Olympic Games in Athens. (AP Photo/Rusty Kennedy)

U.S. Olympic swimmer Natalie Coughlin displays the medals she won while competing in the Athens Olympics during a news conference on the campus of UC Berkeley in Berkeley, Calif., Sept. 1, 2004. (AP Photo/Marcio Jose Sanchez)

Natalie Coughlin celebrates winning the gold in the women's 100-meter backstroke final during the swimming competitions in the National Aquatics Center at the Beijing 2008 Olympics in Beijing. (AP Photo/Anja Niedringhaus)

Australia's Stephanie Rice, left, and Natalie Coughlin of the U.S. celebrate each other after Rice won the women's 200-meter individual medley final with a world record during the swimming competitions in the National Aquatics Center at the Beijing 2008 Olympics. Coughlin won the bronze medal. (AP Photo/Mark J. Terrill)

Women's 4x100-meter freestyle relay silver medal winners of the United States show their medals during the awarding ceremony in the National Aquatics Center at the Beijing 2008 Olympics. They are from left: Natalie Coughlin, Kara Lynn Joyce, Lacey Nymeyer and Dara Torres. (AP Photo/Mark J. Terrill)

U.S. Natalie Coughlin shows her bronze medal after she won the women's 100m Backstroke event at the FINA Swimming World Championships in Shanghai, China, 2011. (AP Photo/Michael Sohn)

Natalie Coughlin competes in the women's 100 meter backstroke preliminaries at the Charlotte UltraSwim Grand Prix in Charlotte, N.C., May 12, 2012. (AP Photo/Bob Leverone)

Natalie Coughlin jumps off the starting block during a preliminary heat of the 100-meter freestyle at the Santa Clara International Grand Prix swim meet, June 1, 2012 in Santa Clara, Calif. (AP Photo/Marcio Jose Sanchez)

Natalie Coughlin warms up before competing in the 100-meter backstroke during the Santa Clara International Grand Prix swimming competition, June 3, 2012, in Santa Clara, Calif. (AP Photo/Marcio Jose Sanchez)

Natalie Coughlin competes in the 100-meter backstroke during the Santa Clara International Grand Prix swimming competition, June 3, 2012, in Santa Clara, Calif. (AP Photo/Marcio Jose Sanchez)