China, an emerging force, narrowly pipped Spain to claim second place, their near-perfect synchronisation score securing the country's best result in the sport and denting Spanish hopes of repeating their silver success earlier this week.
The Russians, who have won every duet and team gold since the Sydney Games, scored 98.93 points out of a possible 100 for their "free" routine, a sequence which is not prescribed and in which swimmers show off their creative and technical skills.
Friday's result, after a routine of drumbeats and aggressive legwork, was added to their top-scoring routine in the team technical round, taking them to a total of 197.03 points. Russia had already won gold in the synchronised swimming duet.
Russia top Olympic synchro scoreboard, Brits sixth
"This has been a lot of work for us all, and you can see that in the tough competition," Russian head coach Tatiana Pokrovskaya said, her hair still dripping after she was thrown in the pool by her celebrating team.
The London Games, though still dominated by Russia, have also stood out for the growing number of serious challengers battling up the synchronised swimming ranks - a long and often arduous journey in a judged sport.
China have shown dramatic improvement under Japanese-born coach Masayo Imura, known as the "mother of synchro" and scored 194.01 points to take the country's first Olympic silver in the sport, with a sequence playing on Asian butterfly themes.
Imura's success has not gone unnoticed in her native Japan, whose own team ends the Games without a synchronised swimming medal for the first time since the sport was introduced at the Olympic Games in 1984.
Spain, silver medallists in the duet segment, were held back at bronze by a fractionally lower synchronisation score than the Chinese, but proved their strength in the artistic stakes with an ocean routine that had spectators roaring.
The swimmers, all of them asked to cut their hair for the occasion, wore caps and swimsuits covered in iron-on, shiny chrome discs that reflected the water and simulated fish-scales.
In the pool, the eight swimmers imitated dolphins leaping, giant crab pincers and fluid waves, wowing the crowd with some of the most daring lifts and leaps of the competition.
Spain took silver in the team segment in Beijing but has since struggled with generational change, losing, among others, 2008 medallist Gemma Mengual, forcing the team to work hard to replicate the experience of rivals like Russia.
"It has been a long time since competition was so tight. The Spanish strength is the artistic part - we need to try and raise the level of the first portion of the score, the technical side," Spanish coach Ana Tarres said.
"Russia has shown an incredible capacity to be clear gold medal contenders from 1998 onwards, producing generation after generation of top-class athletes."
Spain, she confided, also battled nature.
"The Spanish physique is also different to the Russian. Our legs are not as long and our bottoms stick out more - we need to work harder to compensate for this," she said.
Russia now faces its own generational change, losing gold medallist Anastasia Davydova, who came out of retirement to compete in the team segment but will now focus on coaching.
Duet and team swimmer Natalia Ishchenko, dubbed "Michael Phelps in a skirt" at home for her gold medal haul, also brushed off questions about her own future and whether she would push through to 2016.
Britain, swimming their first team final, came sixth with a crowd-pleasing Peter Pan number they hope will propel them to the podium in Rio in four years' time.
Only way is up for GB synchro swimmers
Russia win synchro duets gold at Olympics