With the Paris Olympics less than two weeks away, a question hangs over the Games: Will the Seine River be clean enough for athletes to swim in? Triathlon and marathon swimming are scheduled to take place in the Seine, the city's historic waterway, where it has been illegal to swim for more than a century. Despite the city's efforts to clean up the long-polluted river, the water has tested unsafe for humans in recent weeks, and cleaner on other days.