RIO DE JANEIRO (AP) — No one can stop Russia's mermaids.

That much was clear as soon as Natalia Ishchenko and Svetlana Romashina finished the synchronized swimming duet routine that would win them their fourth career Olympic gold medals on Tuesday, extending one of the longest winning streaks in Olympic history.

Russia has not been beaten in an Olympic synchronized swimming event for 20 years, a streak almost certain to be maintained when Ishchenko and Romashina go for another gold Friday in the team event. They're so far ahead of the rest that the only people who seem capable of putting them under pressure are their own fans back home.

"It's psychologically very hard. We understand that everyone's always expecting us to win," Ishchenko said. "There's very close attention on us, we're always being watched attentively, so we need to be head and shoulders above the rest."

Competing with a mermaid-themed routine, their total score after their final performance was such that second-placed China would have needed an almost impossibly perfect performance to challenge for gold. In the end, Russia won with 194.991 points out of a possible 200. China had 192.3688 and Japan 188.0547.

The Russians have a wealth of resources at their disposal, with advanced training facilities near Moscow and even the services of a composer when they couldn't find the right music for their Olympic routine.

"We wanted to bring it life because we're often being called mermaids," Ishchenko said.

Romashina added: "It seems like we spend more of our time in the water than on land, so people ask us if we're going to grow gills or something."

At the ages of 30 and 26 respectively, Ishchenko and Romashina are much older than many of their opponents — Ishchenko has already retired and come back once — but they are already wondering about pushing on to next year's world championships and yet more medals.

"We always have motivation to continue, we just have to find a reason," Romashina said.