Phelps seemingly had the race in hand, but he coasted to the wall over the final few feet instead of making a final lunge and it cost him.
Le Clos touched the wall 0.05 of a second in front of Phelps, who even though he had to settle for a silver medal equaled the record for most medals won at the Olympics.
The bronze medal went to Takeshi Matsuda of Japan.
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