Simone Manuel and Penny Oleksiak split the gold medal in the women's freestyler 100 metre final as the Campbell sisters Cate and Bronte failed to live up to their pre-race billing.
Cate Campbell had set Olympic records in the heats and semi-finals but her race plan fell apart after the turn, dropping from first to sixth and seeing the winning pair set a new OR with a dead equal 52.70 each.
Sarah Sjostrom took bronze, adding to her gold medal in the 100m butterfly.
Manuel and Oleksiak had qualified third and second-fastest behind Cate Campbell respectively, but the 24-year-old Australian looked to have left them behind after touching the wall 0.12 seconds under her own world-record time.
Bronte Campbell had touched the wall second, but both simply went backwards as Manuel capitalised from third and Oleksiak produced a stunning late surge.
Turning seventh seven hundredths off a whole second behind Cate Campbell, the 16-year-old initially reacted with confusion when seeing the number one next to Manuel's name, before realising that she too would be leaving Brazil with gold.