Despite frantic efforts made by fellow motorists, three of four people travelling in an SUV lost their lives Thursday afternoon when their vehicle plunged into icy waters west of Calgary.

The crash happened on a rural road south of Canmore around 3:30 p.m., with the Ford Escape coming to rest in the Spray Lakes reservoir.

Sue Remmer, a sister-in-law of one of the victims, says two couples were involved in the crash. She identifies the deceased as Jennifer Waugh and her husband Darrin Waugh, both 39, as well as 43-year-old Roddy Allan, who was behind the wheel.

33-year-old Jaimie Waugh, Allan's common-law wife and Darrin's younger sister, survived the collision with minor injuries.

According to Remmer, the lone survivor remembers being pulled out of the vehicle by strangers and was taken to hospital with virtually no marks on her body. She has since been released from the hospital in Canmore and is staying with family in Calgary.

CTV News is told a pair of motorists waded into the water after the crash and pulled two people out of the vehicle before a water rescue team arrived. Police are praising the effort.

"Those people responded to the incident and placed themselves in a certain amount of danger by entering the water," said Sgt. Brad Freer with the Canmore RCMP detachment.

"It's very cold and they offered as much assistance as they could."

Remmer says Jennifer, who is originally from Edmonton, and Darrin, who comes from Innisfail, had been living in Calgary for about 15 years. The two were married eight years ago in Ireland and "were the loves of one another's lives."

She says Roddy and Jamie recently moved back to Cochrane after spending at least a couple years in Ontario. It's believed the two relocated because they wanted to be closer to family as they raised their 11-year-old and two-and-a-half-year-old boys.

"They are a happy and caring couple and great parents," said Remmer.

RCMP moved the SUV to a local impound, where investigators will examine the vehicle in an attempt to determine what caused the crash.

Police are still on the ground searching for a dog that was inside the vehicle during the collision. The pet, named Clancy, is believed to be okay and belongs to one of the victim's friends.

With Files from CTV Calgary