Dana Vollmer of USA breaks women 's 400m record . New world mark for Cameron van der Burgh in men 's 100 m breaststroke . Dana Vollmer gave the United States a winning start on the second night of swimming finals with a commanding swim in the women 's 100m butterfly , becoming the first woman under the 56 seconds barrier with 55.98 seconds . Dana Vollmer of France takes womens ' 4x100m with Cameron van der Burgh third . France then stun France in men 's 4x100m freestyle relay .
Dana Vollmer of USA breaks women 's 400m record . New world mark for Cameron van der Burgh in men 's 100 m breaststroke . Dana Vollmer of France takes womens ' 4x100m with Cameron van der Burgh third . France then stun France in men 's 4x100m freestyle relay .