Canada set two world junior records in the opening day of the world junior swimming championships on Wednesday in Indianapolis. 

Olympians Penny Oleksiak and Taylor Ruck were part of the women's 4x200-metre freestyle relay team that captured gold in a record-setting time of seven minutes, 51.47 seconds. 

The Canadian quartet, which included Kayla Sanchez and Rebecca Smith, were nearly six seconds ahead of Russia and faster than any team of teenagers in history.

Canadian junior women's relay team wins gold, sets world record9:58

"I think it was pretty exciting. Going into the race we were all pretty confident with what times we could go and to come out with the gold medal and a world junior record is pretty awesome," said Oleksiak, who helped the senior team to two relay bronze medals at FINA World Championships in Budapest, Hungary, last month.

"I think it's pretty cool because all four of us train together and we're all super close," added Smith, who was part of one of the Budapest bronzes. "Just to have that team atmosphere is pretty great."

Mabel Zavaros, who helped the team qualify through morning heats as the top seed, also received a gold medal.

It was the second world junior record of the day for Ruck, who also swam the 100 backstroke semifinal in 59.28.

"We all train so well together, we're really a cohesive group of girls," Ruck said. "This is my meet to step out and show what I can do. I feel like this is where I should be, doing these times, so I'm happy with where I am."

Taylor Ruck sets world junior record in 100m backstroke2:44

The new mark sends her to Thursday's final as the top seed, and re-set her own 15-17 Canadian record, which dropped three times Wednesday. Ruck had lowered the mark to 59.64 in the morning session, only a heat after Jade Hannah of Halifax set possibly the shortest-lived record in Canadian history.