APTOPIX London Olympics Swimming Men

Michael Phelps smiles and flashes the 15th gold medal of his Olympic career. (Matt Slocum/Associated Press)

Michael Phelps smiles and flashes the 15th gold medal of his Olympic career. (Matt Slocum/Associated Press)

United States’ Michael Phelps at the Aquatics Centre in the Olympic Park during the 2012 Summer Olympics in London, Tuesday, July 31, 2012. (AP Photo/Matt Slocum)