Schellenberg, 28, had hiked to Juniper Bay beach, along the shore of the glacial lake near Vernon, when she met a mother and her two children playing fetch with their seven-month-old golden retriever puppy, named Lucy.
Schellenberg said the puppy suddenly ran into the lake to chase after several ducks.
"It was swimming for about four or five minutes and the ducks were circling around the lake and bringing the dog further out," she said.
"The owner of the dog and her two little kids were trying to get the dog to come back and it wouldn't come back."
Schellenberg said the puppy started to struggle and dip under the water about 20 to 30 metres from shore.
"This poor little girl was just calling her dog's name trying to get the dog back and it wouldn't [respond]," Schellenberg said. "We got really worried that the dog was going to drown."
That's when she decided to go into the lake to retrieve the young retriever.
"I was thinking of this seven year old girl who was screaming her dog's name and I just couldn't imagine if she had to watch her dog drown that day."
A daring rescue...and a warning
Schellenberg took off her shoes, ran into the water and swam out to the dog.
"I grabbed her collar, and just kind of tucked her under my arm like a football, because she was still fairly small at seven months, and we both swam back to shore," she said.
Vernon RCMP spokesperson Gord Molendyk agreed the story had a happy ending, but he warns against people going into lakes or rivers to save a pet.
"From a police perspective and a safety perspective, the majority of time pets make it back [to shore]," he said.
"In this particular case, perhaps it may not have happened because it was a pup, but we really caution about endangering one's life for that of an animal."
Schellenberg said the young dog quickly recovered once back on shore.
"She kind of coughed and chocked a little bit and recovered and then she was just a happy little puppy," she said.
After the ordeal was over, Schellenberg finally noticed how cold she was.
"[The water] was cold. I wouldn't recommend swimming," she said. "Not yet."