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Michael Phelps (C) dives of off the starting block as he competes in preliminary heat 13 of the Men's 100 m Butterfly during Day Six of the 2012 U.S. Olympic Swimming Team Trials at CenturyLink Center on June 30, 2012 in Omaha, Nebraska. (Photo by Al Bello/Getty Images)

U.S. Olympic swim trials

Athletes compete for a place on the U.S. London Olympic swimming team.