Star swimmers like Phelps and Lochte can't possibly swim in all the preliminary races and still have time to rest for their final races. So there are a bunch of swimmers who take their place in prelim relay races in order to ease the schedule of the stars. Since 1992, swimmers who participated only in the preliminary swims for the relays also win the medal, though they do not get to stand on the podium. Without television coverage, they are the behind the scenes medalists.
This is Charlie Houchin.
Here is Davis Tarwater.
One of the oldest members of the swim team, Jason Lezak.