Russia's Svetlana Romashina claimed her record sixth Olympic gold medal in artistic swimming, teaming with Svetlana Kolesnichenko to win the duet.
The Russians were heavy favourites in a sport they have dominated for more than two decades.
Their last Olympic loss in the sport formerly known as synchronized swimming came at the 1996 Atlanta Games.
Romashina had been tied with fellow Russians Anastasia Davydova and Natalia Ishchenko with five gold medals apiece.
Now, Romashina is in a class by herself after a riveting performance accompanied by the music "Spiders".
The Russian pair received marks of 98.8000 for their free routine for a combined score of 195.9079.
The silver went to China's Huang Xuechen and Sun Wenyan at 192.4499, while Ukraine's Marta Fiedina and Anastasiya Savchuk beat out Japan for the bronze with 189.4620.
Australian Associated Press