Behrent justified her return to the elite level of the sport last year after missing 2014.
The duo now have a chance to create history when they race in the women's eight final tomorrow. No New Zealanders have earned two rowing medals at the same Games.
Earlier, Mahe Drysdale remained on target to win a third Olympic medal and Emma Twigg her first. Both single scullers eased into their respective finals.
Defending champion Drysdale was dominant. The 37-year-old claimed the lead early and extended it before easing off over the last 500m. He won by 2.99 seconds from Stanislau Shcharbachenia of Belarus. Third was Belgian Hannes Obreno, who stunned Drysdale at the Henley Royal Regatta five weeks ago.
The other semifinal was won by four-time world champion Ondrej Synek of the Czech Republic, the London Olympic silver medallist.
He and Drysdale are likely to duel for gold again.
In a possible preview of the women's final, Twigg and Australian world champion Kim Brennan crossed within centimetres of each other.
Brennan won by 0.32s, having opening up a two boat-length lead during the middle stages.
Twigg closed over the last 500m to finish second ahead of Jeannine Gmelin of Switzerland.
"I don't want to show all of my cards, and that's probably given her enough to think about," Twigg said.
The results mean New Zealand have qualified boats for finals in eight of 11 classes entered.
Two-time defending world champions Julia Edward and Sophie MacKenzie finished fourth in the lightweight double sculls behind the Netherlands, Canada and China.
They remained in touch at halfway but slipped to fifth after the third quarter as Canada's Lindsay Jennerich and Patricia Obee made their move.
The Dutch pair of Ilse Paulis and Maaike Head had established a lead at that stage and no one could catch them.
Edward and MacKenzie were 5.88s adrift, and 4.12s shy of China in third.
- AAP
