At the starting dock of the Olympic triathlon trials, the expression on Andy Potts’s face seems to say I will kill you with my eyes. As the starting gun fires, he plunges into the Black Warrior River in Tuscaloosa, Alabama, and, in a burst of white foam, quickly pulls ahead of nine rivals. The second-ranked Hunter Kemper manages to hold pace with Potts for a few minutes, then drifts back into third place.