Just before 9 o'clock on a recent summer morning, temperatures soared near 85 degrees and the air was thick with humidity.

It was perfect swimming weather for the two dozen or so youngsters splashing in the pool at the Old Mill Swim Club in a tree-lined neighborhood in Millersville.

The members of the Old Mill Swim Team tore across the water to see how fast they could make it to the other side as coaches and parents cheered them on. The swimmers were preparing for one of their last meets of the summer.

They take their sport seriously, but it was clear from the laughs that pierced the air that team members also were...