She’s riding a new wave. Yusra Mardini, 17, was one of the million-plus refugees who headed for Europe last year, fleeing her native Syria in a boat stuffed with about 20 others. When the engine died and the vessel started taking on water, she and her sister jumped overboard. Together they swam and pushed the boat for three and a half hours until it reached Lesbos safely. Now Mardini, who found refuge in Germany, is among 43 migrant athletes looking to compete in the Rio Olympics this summer.